refactor(build): simplify and modularize

simplify:
- use same html file for dart and JS
- build benchmarks automatically when doing `gulp build`
- centralize configuration

modularize:
- move all build tasks into separate node.js modules under
  `tools/build`.

changes:
- the `build` folder is now the `dist` folder

Closes #284
fix(view): fix DirectivePropertyGroupMemento to return a new group instead of null
cleanup(view): remove unused code
chore(docs): fix docs/watch task name
chore(docs): add code prettification

Closes #285
chore(docs): refactor traceur usage
fix(change_detector): adding new ranges when disabling the current enabled record
refactor(change_detector): moves enableRecord/disableRecord into the Record class