add option to choose different player before game play starts

[cch5ng]

• need to style the Start button;
• need to also apply logic so that the user selected avatar shows when the game starts

[cch5ng]

need to refactor b/c some of the canvas click logic is already defined in the app. but not exactly sure how much interaction should be defined in engine vs app.

[cch5ng]

in v4, made changes mainly to app.js (new Avatar object). and minor updates to engine.js. but wonder if it could have been done better, like using css borders rather than creating additional graphics. is it better to do DOM manipulation thru js for the pre-game start screen or to be consistent and use the canvas. probably push to master and gh-pages but these changes will not be reflected then in geolocation branch

[cch5ng]

made the merges to gh-pages and master. closing for now.