Added function documentation

-Modified calculator.lua to have a luadoc style comment for calculator
Finished implementing functionality of calculator

-Changed helper functions to be local functions
-Implemented error checking for bad inputs
Removed excess lunit files
Removed excess lunit files
Revert "Removed excess lunit files"

This reverts commit 01358b3a48480aeb1908824be8a4b657c85b58ce.
Removed error checking because

-I want conflict for you guys
Deleted arbitrary lunit
Updated README, test.lua

-Fixed specifications as depicted in the README
-Added bad input test for test.lua
Updated README, test.lua

-Fixed specifications as depicted in the README
-Added bad input test for test.lua
Fixed bug in test.lua and changed default behavior in calculator

-If the operator does not exist, return error instead of nil
-Fixed bug in test.lua with pcall
Fixed bug in test.lua with call to pcall
Merge branch 'documentation' into functionality

Conflicts:
	calculator.lua
This commit details a change in calculator.lua as a result of a merge of documentation into functionality.

  -delated conflicting lines from calculator.lua in documentation which had no real code written
  -removed unecessary comments from calculator.lua in documentation
Merge branch 'functionality'

Conflicts:
	calculator.lua
Changed calculator.lua so that functionality could be merged.

  -removed skeleton code from master branch