basic api gem

Here is the implementation I started based on Zencoder's ruby gem's design and following Leetchi's API specifications. I added a basic readme and a basic set of unit tests.

*Future improvement:*
- the resources folder could be completed
- the configuration could be improved (actually simply using ENV variables)
- unit tests could be greatly improved to better cover the API (hopefully it will be easier when the new documentation will come out ^^)
- resources methods could be documented