Small code changes to be able to import yowsup from other scripts

These changes allow **yowsup** to be used from other python scripts as easy as this:

    import Yowsup
    credentials = ('', 'xxx', 'xxx', 'xxx') #same from config.file
    args = {'send': [destination_number, message], 'v1': False,'wait':False,'debug':False}
    Yowsup.yowsup(credentials,args)

and that's it.

*PD: ofcourse, for this to work, yowsup-cli would have to be renamed to Yowsup.py*