Merge pull request #21 from mygamelife/master

Modified StringObject
Merge branch 'master' of https://github.com/Raydivine/Calculator
Merge pull request #22 from mygamelife/master

Added Calculator.c , test_Calculator.c and modified StringObject
Merge branch 'master' of https://github.com/Raydivine/Calculator
Merge pull request #23 from mygamelife/master

Merged Evaluate.c and getToken
Merge pull request #25 from banana93/master

Done editing
Modified the handle_ENTER function in command_prompt.c and completed the code in main.c
Merge pull request #26 from darklord1310/master

Combined all the code together in main.c
modify  evaluatePostfixesAndInfix(), and add operation for the case  there is prefix operator inside the bracket
Trying tokenDisplay
Conflict resolved
Update the command line interface

Added features:
  - It can display the type of error of input
  - It can specify the location of error