Add Garmin's TCX V2 sample fitness history details TCX file.

Source: http://developer.garmin.com/schemas/tcx/v2/
Basic public API allowing you to instantiate a TcxFile object with tcx data.
Peding spec for public accessors on Tcx::TcxFile.
Add CodeClimate test coverage reporter
Add ox gem
Parse TCX file, making basic pending tests pass.
Merge pull request #2 from aerobicio/parse-active-duration-and-distance

Parse active duration and distance