Fixes numenta/nupic.cerebro2#61. Namespacing.

Fixes #61.
 
Attention: @chetan51

Namespaced all global objects under Cerebro2. Also wrapped main.js code in anonymous functions to prevent global namespace pollution. This fixes the issue described in numenta/nupic.cerebro2#61 where, in the Chrome browser, the "history" object cannot be overwritten.