First skeleton for the TweetManager.scala

First skeleton for the TweetManager, with the following functions:
	1/ StartAll(queries)
	2/ StopAll (queries)
First implementation of the TweetManager

- First implementation of the TweetMananger, for now based only on the Twitter
Search API. Will be changed in a few time to include the Streaming API.

- Addition of tests in TweetStreamerSpec for examples.
Merge branch 'master' of https://github.com/TweetAggregator/TweetAggregator