Request.get_normalized_parameters() is sorting and encoding parameters in the wrong order.

[gorakhargosh]

The OAuth 1.0 spec at http://tools.ietf.org/html/rfc5849#section-3.4.1.3.2
clearly states that the encoding is done before the sorting.
python-oauth2 sorts before encoding. Also the tests for this routine
are incorrect.

Please fix this line to sort after encoding.
https://github.com/simplegeo/python-oauth2/blob/master/oauth2/__init__.py#L476

Cheers!
Gora Khargosh.

[gorakhargosh]

A comparison of query string generated by python-oauth2 (left)
versus what's expected (right).

http://twitpic.com/5gs8z5/full

>>> sorted(["c%40", "c@", "c2"])
['c%40', 'c2', 'c@']