add support for Retrolink N64 controller on Firefox and WebKit
Fixes regression in `WebKitPlatform.factory`.

Some `gamepadGetter` functions were returning the browser's gamepad
inquiry function instead of the gamepad list returned by that function.
Adds regression tests and fixes the issue.
Updates button getter for new GamepadButton API.

Modern Firefox has aligned with the W3C Gamepad API spec, which
calls for gamepad.buttons to be an array of GamepadButton objects
rather than button state values. This adds support for that API.
Bug fix for WebKit browsers.
Added script to run grunt without installing it globally.
Improved Firefox support.
Updated tests, compiled file and docs.
Merge pull request #26 from bassarisse/master

Bug fix and Firefox support
Merge branch 'firefox_api_update' of https://github.com/mildmojo/HTML5-JavaScript-Gamepad-Controller-Library into mildmojo-firefox_api_update

Conflicts:
	gamepad.js
	gamepad.min.js
Merge branch 'n64' of https://github.com/cvan/HTML5-JavaScript-Gamepad-Controller-Library into cvan-n64

Conflicts:
	doc/classes/Gamepad.html
	doc/data.json
	doc/files/gamepad.js.html
	gamepad.js
	gamepad.min.js
Merge pull request #27 from kallaspriit/mildmojo-firefox_api_update

Mildmojo firefox api update
Merge branch 'master' into cvan-n64

Conflicts:
	doc/classes/Gamepad.html
	doc/data.json
	gamepad.min.js
Merge branch 'cvan-n64'
Adds mapping for Dualshock 4 controller in Firefox.

Chromium seems to directly support the PS4 Dualshock 4 controller,
but Firefox has some really strange mappings. This adds correct
mappings for the DS4 controller under Firefox.

Tested in Firefox 29 for Linux.