Fix button wrapping on small (mobile) screens

Ensure the ASC and SHA buttons on the downloads page get wrapped
together when the screens are small, and that they don't merge into the
next artifact's buttons and get mangled.
diff --git a/pages/downloads.md b/pages/downloads.md
index db0a591..2cb6147 100644
--- a/pages/downloads.md
+++ b/pages/downloads.md
@@ -58,8 +58,10 @@
 {% assign glyphSave = '&nbsp;<span class="glyphicon glyphicon-cloud-download"></span>' %}
 {% assign glyphLock = '&nbsp;<span class="glyphicon glyphicon-lock"></span>' %}
 {% assign srcbinArray = 'src bin' | split: ' ' %}
-{% assign btnStyleDefault = 'class="btn btn-default" style="text-transform: none; font-family: monospace"' %}
-{% assign btnStylePrimary = 'class="btn btn-primary" style="text-transform: none; font-family: monospace"' %}
+{% assign btnDownloadStyle = 'class="btn btn-primary" style="text-transform: none; font-family: monospace"' %}
+{% assign btnSigStyle = 'class="btn btn-default" style="font-family: monospace"' %}
+{% assign btnHashStyle = 'class="btn btn-default" style="font-family: monospace"' %}
+{% assign btnDocStyle = 'class="btn btn-default" style="text-transform: none; font-family: monospace"' %}
 
 ## Current Releases
 
@@ -71,22 +73,24 @@
 current generation, containing the newest features, bug fixes, performance
 enhancements, and more.
 
-<div class="row btn-group" style="padding-left: 75px">
 {% for srcbin in srcbinArray %}
 {% assign lnkFile = 'accumulo-' | append: linkVers | append: '-' | append: srcbin | append: '.tar.gz' %}
 {% assign lnkSuffix = '/accumulo/' | append: linkVers | append: '/' | append: lnkFile %}
-  <a {{btnStylePrimary}} href="{{closerLink}}{{lnkSuffix}}" link-suffix="{{lnkSuffix}}">{{lnkFile}}{{glyphSave}}</a>
-  <a {{btnStyleDefault}} href="{{downloadsLink}}{{lnkSuffix}}.asc">ASC{{glyphLock}}</a>
-  <a {{btnStyleDefault}} href="{{downloadsLink}}{{lnkSuffix}}.sha512">SHA{{glyphLock}}</a>
-  <br>
-{% endfor %}
+<div class="row btn-group" style="margin-left: 70px">
+  <div class="col btn-group">
+    <a {{btnDownloadStyle}} href="{{closerLink}}{{lnkSuffix}}" link-suffix="{{lnkSuffix}}">{{lnkFile}}{{glyphSave}}</a>
+  </div><div class="col btn-group">
+    <a {{btnSigStyle}} href="{{downloadsLink}}{{lnkSuffix}}.asc">ASC{{glyphLock}}</a>
+    <a {{btnHashStyle}} href="{{downloadsLink}}{{lnkSuffix}}.sha512">SHA{{glyphLock}}</a>
+  </div>
 </div>
-<div class="row btn-group-sm" style="padding: 25px; padding-left: 50px">
-  <a {{btnStyleDefault}} href="{{site.baseurl}}/release/accumulo-{{linkVers}}">Release Notes</a>
-  <a {{btnStyleDefault}} href="https://github.com/apache/accumulo/blob/rel/{{linkVers}}/README.md">README</a>
-  <a {{btnStyleDefault}} href="{{site.baseurl}}/docs/2.x">Online Documentation</a>
-  <a {{btnStyleDefault}} href="https://github.com/apache/accumulo-examples">Examples</a>
-  <a {{btnStyleDefault}} href="{{site.baseurl}}/docs/2.x/apidocs">Java API</a>
+{% endfor %}
+<div class="row btn-group-sm" style="margin: 25px; margin-left: 50px">
+  <a {{btnDocStyle}} href="{{site.baseurl}}/release/accumulo-{{linkVers}}">Release Notes</a>
+  <a {{btnDocStyle}} href="https://github.com/apache/accumulo/blob/rel/{{linkVers}}/README.md">README</a>
+  <a {{btnDocStyle}} href="{{site.baseurl}}/docs/2.x">Online Documentation</a>
+  <a {{btnDocStyle}} href="https://github.com/apache/accumulo-examples">Examples</a>
+  <a {{btnDocStyle}} href="{{site.baseurl}}/docs/2.x/apidocs">Java API</a>
 </div>
 
 
@@ -97,22 +101,24 @@
 The most recent legacy (1.x) release of Apache Accumulo&reg; is version
 {{linkVers}}.
 
-<div class="row btn-group" style="padding-left: 75px">
 {% for srcbin in srcbinArray %}
 {% assign lnkFile = 'accumulo-' | append: linkVers | append: '-' | append: srcbin | append: '.tar.gz' %}
 {% assign lnkSuffix = '/accumulo/' | append: linkVers | append: '/' | append: lnkFile %}
-  <a {{btnStylePrimary}} href="{{closerLink}}{{lnkSuffix}}" link-suffix="{{lnkSuffix}}">{{lnkFile}}{{glyphSave}}</a>
-  <a {{btnStyleDefault}} href="{{downloadsLink}}{{lnkSuffix}}.asc">ASC{{glyphLock}}</a>
-  <a {{btnStyleDefault}} href="{{downloadsLink}}{{lnkSuffix}}.sha512">SHA{{glyphLock}}</a>
-  <br>
-{% endfor %}
+<div class="row btn-group" style="margin-left: 70px">
+  <div class="col btn-group">
+    <a {{btnDownloadStyle}} href="{{closerLink}}{{lnkSuffix}}" link-suffix="{{lnkSuffix}}">{{lnkFile}}{{glyphSave}}</a>
+  </div><div class="col btn-group">
+    <a {{btnSigStyle}} href="{{downloadsLink}}{{lnkSuffix}}.asc">ASC{{glyphLock}}</a>
+    <a {{btnHashStyle}} href="{{downloadsLink}}{{lnkSuffix}}.sha512">SHA{{glyphLock}}</a>
+  </div>
 </div>
-<div class="row btn-group-sm" style="padding: 25px; padding-left: 50px">
-  <a {{btnStyleDefault}} href="{{site.baseurl}}/release/accumulo-{{linkVers}}">Release Notes</a>
-  <a {{btnStyleDefault}} href="https://github.com/apache/accumulo/blob/rel/{{linkVers}}/README.md">README</a>
-  <a {{btnStyleDefault}} href="{{site.baseurl}}/1.10/accumulo_user_manual">User Manual</a>
-  <a {{btnStyleDefault}} href="{{site.baseurl}}/1.10/examples">Examples</a>
-  <a {{btnStyleDefault}} href="{{site.baseurl}}/1.10/apidocs">Java API</a>
+{% endfor %}
+<div class="row btn-group-sm" style="margin: 25px; margin-left: 50px">
+  <a {{btnDocStyle}} href="{{site.baseurl}}/release/accumulo-{{linkVers}}">Release Notes</a>
+  <a {{btnDocStyle}} href="https://github.com/apache/accumulo/blob/rel/{{linkVers}}/README.md">README</a>
+  <a {{btnDocStyle}} href="{{site.baseurl}}/1.10/accumulo_user_manual">User Manual</a>
+  <a {{btnDocStyle}} href="{{site.baseurl}}/1.10/examples">Examples</a>
+  <a {{btnDocStyle}} href="{{site.baseurl}}/1.10/apidocs">Java API</a>
 </div>