Add jslint indent variable
Switch to jshint

* Less picky about some pointless things

* Modify info at top of file: remove indent specification and add
  "browser: true" so that browser variables are declared.
Add global class name includes for jshint
Add helper_functions.js file
Simplify canMerge logic
Add helper function for setting default args
Add function for counting tiles
Use more standard whitespace since we are using jshint

(had to have spaces between 'function' and '()' for jslint)
Separate value generation functions from GameManager

Allows for easier switching of the method for generating values.