Fixed close() exception when using new Apache libraries

**Problem**
I was using the 'latest' Apache client for my application. Using this version threw an IllegalStateException whenever I tried to close the connection to a GAE server (not development).

**Exception Message**
Invalid use of BasicClientConnManager: connection still allocated.

**Solution**
I updated the library dependencies and migrated to use HttpClientBuilder to create a default http client instead of the now deprecated DefaultHttpClient.

close() doesn't throw an exception anymore.