Implemented LinkedInDeveloperAuthentication class that stores the 4 credentials necessary for an OAuth 1.0a flow and modified LinkedInApplication to use requests_oauthlib to do all of the heavy lifting in enabling the OAuth 1.0a flow that requires no redirects or user intervention in the event that it is passed a LinkedInDeveloperAuthentication instance. Very useful for situations in which users just want to access their own data or when developers are testing. Have not updated the README docs yet