.net 4.5, bugs, and removed deprecated data

* removed the deprecated "active score" that Fitbit removed from the API
* moving the project to .NET 4.5 in prep for adding XXXXAsync version of
all calls (yes, it's coming -- async is awesome)
* Added in IFitbitClient so you can mock / test this client (duh, why
did this take so long?)
* Fixed a "bug" in GetWeight that attempted to get any range of weight.
No no, the Fitbit API only allows weight endpoint to do 31 days at a
time unless you do a timeseries single-data type call
* changed the sample MVC project to show more endpoints and not
ActiveScore since it was removed