Delegate the loading of tweets to the client

Also fixes the problems caused by https://github.com/nerdzeu/nerdz.eu/commit/8a5e733a2135e644e317fa71693abaa90d5631fe.
Since the loading of tweets is now client-based, you must remove the 'tmp/twitter_cache' folder.
NOTE: this commit adds a workaround for an issue found with the onload handler, which involves a small patch to the messages class. You can find more details in the Javascript class file.
Fix Twitter once and for all.
Merge pull request #199 from Robertof/master

Delegate the loading of tweets to the client