Changed the order board tiles are placed to make it easier to check if 6s or 8s are next to each other
Added the 6/8 adjacency checking.  Still need to implement test cases.
Fixed some missing parentheses
Fixed an error where the desert tile was not being handled properly in the roll tile checking, added test cases for the roll tile checking
Board should no longer allow 6s or 8s next to each other.  Test cases are written, but I wasn't sure how to run them to test...
Finished polishing roll checking tests
Merge branch 'master' into serialization

Conflicts:
	include/GameBoard.h
	tests/test_GameBoard.cpp