(Try to) set up redirect to zipkin.io

Since Zipkin withdrew from the incubator.
diff --git a/.htaccess b/.htaccess
new file mode 100644
index 0000000..d5787a9
--- /dev/null
+++ b/.htaccess
@@ -0,0 +1,3 @@
+RewriteEngine on
+RewriteCond %{HTTP_HOST} ^zipkin.apache.org [NC,OR]
+RewriteRule ^(.*)$ https://zipkin.io/$1 [L,R=301,NC]