Updated integer regexp to allow for negatives

Found this while looking for TODOs

Implemented [this](http://stackoverflow.com/questions/16774064/regular-expression-for-whole-numbers-and-integers) pattern instead.  Added a unit test and it seems to be working.
No, I can't explain it  : ) I'm not the best with these.  I was going off of the SO link I found + the unit test.