Added new menu in the UI for key mapping in index.html.
Modified default.css to correct the size of the background in the menu.
Added setKeyMappingMenu() and setKey(event) functions to ui.js, to respectively create the menu and send the event that a new key is wanted for an action.
Added the setKey command to the setMessageTriggers() function in trigger.js to match the new UI elements.
Added the mapKeyToControl(action,keyCode) function to trigger.js, to add the new wanted key (given by keyCode) to an action, remake the window.controls object and update the events handler by redoing proliferate.
Fix : Correction on the key mapping menu for Chrome

Added correction in default.css to improve the look of the menu in Chrome and fix the breaking on the Sprint button.
Improvement for the pull request

Added a background color for the selected button in the key mapping menu.
The input button now use the Press Start font like the UI.
Fixed mouvement of the KeyMapping menu when Option was selected

Added a quick fix on the css of the in_options element. The z-index property is set to -1 to force the "- Options -" label to be displayed.
Merge pull request #131 from Umigatsu/master

Added support for changin keys #24
Documentation for sprites

Hurray!