Pin connection_pool gem

- Address asset precompile error - wrong number of arguments

Author: nomadicoder

Gemfile

@@ -62,5 +62,5 @@ end
 # Required for memcached
 group :production do
   gem "dalli"
-  gem "connection_pool"
+  gem "connection_pool", "~> 2.4"
 end

Gemfile.lock

@@ -123,7 +123,7 @@ GEM
       logger (~> 1.5)
     coderay (1.1.3)
     concurrent-ruby (1.3.6)
-    connection_pool (3.0.2)
+    connection_pool (2.5.5)
     coveralls (0.7.1)
       multi_json (~> 1.3)
       rest-client
@@ -580,7 +580,7 @@ DEPENDENCIES
   bootstrap
   brakeman
   capybara
-  connection_pool
+  connection_pool (~> 2.4)
   coveralls
   cssbundling-rails
   csv