Corrected app delete example code.

Actual function call is app.delete(). Changed the readme to reflect that.
add support for configuring an addon when adding it via params dict, as per heroku.rb i.e. cloud.app.add('deployhooks:http'
, params={'url':'http://myawesomeapp.herokuapp.com'})
Merge pull request #26 from gabrtv/master

Remove debug print
Merge pull request #24 from wcdolphin/master

Add support for configuring an addon when adding it.
Merge pull request #23 from skoczen/patch-1

Corrected app delete example code.