Sync versions of all calls

[aarondcoleman]

While it might not be a priority or feasible for this project adding in non-async versions of each call would allow us in the Fitbit.NET library (https://github.com/aarondcoleman/Fitbit.NET) to replace all our OAuth code and maintain our existing APIs while adding in async versions all relying on this one project. Ideally all the method names would have been done with the XxxxXxxxAsync() style in this project, but they aren't so perhaps there's another way to group sync versions with their async counterparts.

If there's a similar project that is also PCL OAuth we might use please let me know.