Support for JSON Response Format and Fitbit Partner API

* API+: getIntradayTimeSeries
* API+: setResponseFormat
* Improvement: support for json response format
* Bugs: default parameters for getWater and getHeartRate
* Bugs: minor bugfixes to put this thing together

Signed-off-by: James G. Kim <jgkim@jayg.org>
fixed a typo bug causing parsing error

Signed-off-by: James G. Kim <jgkim@jayg.org>
Merge pull request #1 from jgkim/master

Support for JSON Response Format and Fitbit Partner API