Fixed loading of clay library.

Add: clay.js to wrap the clay io initalization and scripts loading.
Add: leaderboard check in hiscore calls. If leaderboard was not
initialized an error message will be displayed on the hiscore board.
Change: Changed the way bootstrap.js is loaded. Now loaded right after
require.js initializes. clay.js loading is triggered from bootstrap.js.
Added leaderboard instance check on hiscore.save().