[feature] Adding Twitter support

This commit initiates Twitter support. It imports some important
classes, that are related to request signing. It also relayout
tools and tests, and prepare the tools to generate classes for
any social network.

This commit also includes a Twitter test that should be able to
perform PIN based authentification.
Initial work on TwitterInterface

This commit includes some initial work on TwitterInterface
to provide a Twitter specific subclass of
SocialNetworkInterface.

It provides initial support of TwitterUserInterface, and
includes the capability to query followers and followe.
Added tweet support

This commit adds tweet support, including the
capability to list an user's tweets, the home
feed for the logged user, and the capability
to RT / (un)favourite / post / reply to tweets.
Merge pull request #22 from SfietKonstantin/twitter

[nemo-social] Add support for Twitter