Grammar changes; passes testcases 1,2,3,4,5,6,7,9,10 (#39)
INTLIT and FIXEDPTLIT now parse rules to properly handle MINUS
Fixed bug where an array can be declared with negative size
Grammar correctly fails testcases 8, 9 gracefully (#39)
Merge pull request #40 from CS4240-tiger/testcase-gram-check

Rewrite of grammar to pass testcases 1, 2, 3, 4, 5, 6, 7, 10 and gracefully fail 8, 9