Branch:dec - adding return statement to all the decorator func

[davislx]

Bug

The client/token getter and setters in oauth provider 1 & 2 makes the original function not callable

Reproduce

Steps:

from . import oauth  #the oauth server object
@oauth.grantgetter
def load_request_token(token):
     print 'abc'
     return 1

if __name__ == '__main__':
    load_request_token('cba')

Expectation:
Running the script will print out abc

Reality:
Won't be able to call load_request_token

Solution

Add return f to all the getter and setter in the providers

Reference

Flask's getter decorator also return the f:

@setupmethod
def before_request(self, f):
    """Registers a function to run before each request."""
    self.before_request_funcs.setdefault(None, []).append(f)
    return f

https://github.com/mitsuhiko/flask/blob/master/flask/app.py#L1194

Test result

(flask-oauthlib)davislx@vm-0:~/Github/flask-oauthlib$ nosetests                                                                                                                                              
..................................................................
----------------------------------------------------------------------
Ran 66 tests in 194.731s
OK