Updated MapMyFitness strategy's client_options

The current openauth-mapmyfitness gem by Yeeland Chen is out of date.
The client_options have been updated based on the current MMF API's
Overview pdf as per the following:
- The API's base site path is http, not https
- The auth path is now https://www.mapmyfitness.com/oauth/authorize/
- The http_method should be :post not :get
- The scheme should be :body for url form encoded in body of POST req
- Updated base site url to include /3.1 and removed default sub paths