Test Cases for Activity

Added Test Cases for the Activity Class. Also add a default constructor
of activities because there wasn't one....
Test Cases for Comments

Wrote test cases for the comments class, Fixed a few missing things in
the Activity Test Cases. (the @Before and @Test) (I know how to write
test cases) (No i dont)
Merge pull request #37 from SixAppeal/kyle_unit_tests

Added Tests for Activities and Comments