Removed Chains.add and Chains.remove
Replaced Grid constructor with loader.

Grid is singleton. Ctor not needed.
Major update. Level up/down. Responsive layout.

Implemented level up/down.
  Grid sizes 3x3 up to 10x10 are available.

Application made responsive to window resize.
  Game grid spans largest visible square.
  O-X font on grid cells is auto-resized.

Upgraded bootstrap to 3.0.0
Highlight chains of length > 3.
Smaller font-size for O-X