Use HTTPS instead of HTTP to resolve dependencies

This fixes a security vulnerability in this project where the `pom.xml`
files were configuring Maven to resolve dependencies over HTTP instead of
HTTPS.

Signed-off-by: Jonathan Leitschuh <Jonathan.Leitschuh@gmail.com>
diff --git a/pom.xml b/pom.xml
index 3411f30..8bb88dd 100644
--- a/pom.xml
+++ b/pom.xml
@@ -42,7 +42,7 @@
       </snapshots>
       <id>bintray-allenai-maven</id>
       <name>bintray</name>
-      <url>http://allenai.bintray.com/maven</url>
+      <url>https://allenai.bintray.com/maven</url>
     </repository>
   </repositories>
   <pluginRepositories>
@@ -52,7 +52,7 @@
       </snapshots>
       <id>bintray-allenai-maven</id>
       <name>bintray-plugins</name>
-      <url>http://allenai.bintray.com/maven</url>
+      <url>https://allenai.bintray.com/maven</url>
     </pluginRepository>
   </pluginRepositories>