Port PEG JavaScript to CoffeeScript.
Fix documentation.
Fix return type in documentation.
Remove unnecessary private method.
Use string interpolation for error message.
Fix issues with reporting line and column.
Add note about property assignment.
Fix documentation formatting.
Provide CoffeeScript class with error information.
* Allows access at any time without continually needing to pass line,
  column, etc to instance methods.
Merge pull request #9 from the-gss/peg-coffee

Port PEG JavaScript to CoffeeScript.