Split src/environment.js into Node/browser versions

src/environment_browser.js:
  Use global variables instead of requiring modules. This undoes the effects of
  the following commits, removing ~1KB from the bundle size:
    51003e3: Timers: require('timers') instead of directly using global
    8baf989: LoggerFactory: require('console') instead of directly using global
    b69fef8: Utils.Promise = global.Promise || require('promiscuous');

src/environment.js:
  Export a Node-compatible environment by extending the browser environment
  with the modules listed above.

Gruntfile.js: Tests polyfill Promise using promiscuous-browser.js