Big refactor

- Add a vendor namespace
- Use PSR-* standards http://www.php-fig.org/
- Add the require of php 5.3 at composer.json (removed the use of array short syntax just in one place that forced the "user" to have 5.4)
- Lower the requirements of guzzle to make Unbabel SDK compatible with other SDK's that use Guzzle 3 (eg: AWS SDK)
- Remove all the nonsense global variables and environment stuff
- Remove the use of static just hurt others code, making possible to use dependency injection, forcing developers to write their own wrapper around Unbabel SDK to keep a sane code
- Write proper PHPdoc's
- Remove too much if's and change to switch or sensible defaults
- Use exceptions instead of null returns

Stuff that should be done but didn't had time:
- Unit tests
- Not use the Guzzle functions instead use Guzzle OOP regular client