Lower startup time

Use custom elements  for internal views and minimize reflows to speed up activate time.

This drops **30-40ms** off Atom startup time when editors are already open.

This shouldn't be merged until Atom 0.128 is released since it depends on unreleased methods.

Although `atom.workspaceView.statusBar` no longer extends `View`, I've still left it wrapped in a `$()` so that it still has the jQuery API until we want to break that for 1.0.

Also left in support for old events which can be removed in 1.0.

Closes #34