Added parallel support to ApiClient

It is now possible to make parallel requests using ApiClient. It used typhoeus to handle the requests and typhoeus make the requests in threads, so to get the response and initialize objects with it, is necessary to initialize the objects prior to the block and specify the objects on the requisitions.

View README for further informations. 

@fernandes @gvillalta99 @silviolrjunior @mfbmina  I just mentioned you, so you could watch the birth of a new version of ApiClient. =D