changed exception handling, finished unit testing

-done with unit testing for all of my classes (AvailabilityController,
UserController, Availibility, DateRange) or at least what i plan to do
-changed how exceptions are handled. all exceptions generated in my
controllers should post to the logs and throw an appropriate HttpStatus
-when exceptions are somewhat predictable the HttpStatus should fit the
exception, when not caught the default status is bad request (400)
-added comments to the unit tests
-still need to do integration testing but not right now
Merge branch 'master' of https://github.com/joubin/CSC191