Feature/create client

if I change config.py to directly access the dictionary without using the dict 'get' method a KeyError will be raised if there is no value letting the user know which value is missing. So if there were no attribute called TOKEN for example in the secure.py file, config would throw a KeyError like this:

Traceback (most recent call last):
  File "test_run.py", line 2, in <module>
    from canvas_sdk.client import CanvasClient
  File "/Users/epp785/Documents/workspace-ggts-3.1.0.RELEASE/canvas_python_sdk/canvas_sdk/client.py", line 6, in <module>
    import config
  File "/Users/epp785/Documents/workspace-ggts-3.1.0.RELEASE/canvas_python_sdk/canvas_sdk/config.py", line 13, in <module>
    AUTH_HEADER = {'Authorization ': 'Bearer %s' % SECURE_SETTINGS['TOKEN']}
KeyError: 'TOKEN'

Is that along the line of what you are thinking?