Allowing kwargs to be passed to requests methods.

.gitignore - now ignoring 'env' directory. For virtualenvs being stored
in the same directory.

core.py - updated 'get_nonce' and 'send_ws_request' functions to accept
any number of keyword arguments (kwargs) that are then passed right to
the appropriate 'requests' methods. The interface may have seemed to
change, but where 'headers' was specified before, it is now just handled
by the 'kwargs' argument. This should not change the way it is being
called. The 'timeout' arg what was previously added to the
'send_ws_request' function is now just part of 'kwargs' also.

test/test_byu_ws_sdk.py - Added two new tests to test both the
'get_nonce' and 'send_ws_request' methods.
Updated 'get_ws_session' function with kwargs.

core.py - Updated the 'get_ws_session' function to also accept 'kwargs'
to then be passed directly to the 'requests' methods being called
within.

  If a 'header' kwarg is sent, it is updated with the specific header
  settings, for Content-type, that are needed to make the request.

  The previous function signature had a 'timeout' arg that could be sent
  to indicate when the session should expire. This conflicts with the
  'requests' methods 'timeout' that indicates how long to wait before
  returning anyway. Because of this 'timeout' is now 'casTimeout'. This
  will __break backwards compatibility__, but allows for all of the
  arguments to be sent to the underlying 'requests.post' call.

test/test_byu_ws_sdk_with_input.py - I decided to create a separate test
suite for testing the 'get_ws_session' function, because of the need to
enter a net_id and password. You can run all tests as normal and be
stopped to enter a net_id and password to test, or you can run:

	`python setup.py test -s byu_ws_sdk.test.test_byu_ws_sdk`

to run all the other tests that don't require input.
Added `authorize_request` function.

The `authorize_request` function takes the requested url and the value
given in the Authorization header, among several other arguments, and
determines if the request was properly authorized. Returns the personId
of the valid authorization or None if not properly authorized.

This function could be used in decorators or just by calling from web
service code to determine if the requester is authorized to make
requests to your service. The valid personId can be checked against an
authorized personId list or just if it isn't None to allow all
authorized callers from OIT/BYU.

Note: This method works great for me and the way I need to check
requests. I don't know a ton about all the possible ways of
authorization checking, so this might not work for all cases.

Also added two tests for this function. One that should fail and one
that should success, given correct credentials on test execution.
Merge pull request #7 from byuhbll/master

Taking advantage of the power of `requests`