Merge pull request #32 from jasonchuah93/master

Replace test intepret.c
Merge pull request #33 from jasonchuah93/master

Finally finish all lolzzz
Merge pull request #34 from jasonchuah93/master

 Deleted unecessary things inside the files
Finalize everything
Merge pull request #35 from jasonchuah93/master

Add condition to determine numberStack is NULL anot
Merge pull request #36 from jasonchuah93/master

Add tests for tryEvaluate functions at test_tryEvaluate.c
Merge pull request #39 from jasonchuah93/master

Resolve the 3 issues raised by Dr Poh
Merge pull request #42 from jasonchuah93/master

Make changes in tryEvaluate.c and test_OperatorInfixEvaluate
 Recode tryEvaluateAndExecutePostfix