Handle 'category' property in context.contextActivities
Build 0.21.1
Make 'category' usage throw exception in 0.9 and 0.95

* Requires updates to the LRS methods which didn't previously expect
  statement version conversion to cause exceptions, they need to be
  handled by the "allowFail" code
* Added unit tests around the LRS .saveStatement(s) methods
* Couple of other minor fixes
Build 0.22.0
Merge pull request #60 from brianjmiller/master

Handle 'category' as part of contextActivities