Cleaned up code, abstracted image/board creation

Reduced number of canvas creations to one.
Added game to namespace
Added ids to tds and imgs
Added classes to tds, imgs.

Added example of how to bind to clicks and get ids
Added '|' as a separator for ids.
Added getIndex function and made an empty slot.
Added clicks counter.
Added valid move checker.
Added width/height text boxes.
Renamed main.js to puzzle.js