ImageFactory OAuth request support

https://github.com/aeolus-incubator/tim/issues/95

Adds in the ability to use 2 Legged OAuth for securing
requests to imagefactory.

To test.  Simply turn on OAuth when running factory (i.e. Do no include --no_oauth).  The Factory default settings are:

consumer_key: "mock-key"
consumer_secret: "mock-secret"

Add the appropriate configuration in the Tim initializer.  A default configuration is already present in the initializer and commented out.