Update LinkedIn to use OAuth2

Update linkedin library with the latest version from : https://github.com/ozgur/python-linkedin/commit/a810f430752b1c67f19ce6e4f9ffec991c9a61e5

also pull requests v.1.2.0 to be used with linkedin library.

Most of the changes are from those two libraries. I only updated a little bit of code in boilerplate/handlers.py