Update OOjs UI to v0.1.0-pre (837b2f733e)

New changes:
d40dd30 build: Update grunt-contrib-uglify to v0.6.0
0d89c99 test: Load a theme for the test HTML file so the tests don't fail
f245aa4 Element: Remove test for deprecated onDOMEvent()
cd15f18 Follow-up I730e3d7d: Tab not spaces
a923881 build: Use Karma instead of grunt-contrib-qunit
381864c build: Use Chrome and Firefox for tests instead of PhantomJS
044faa5 Follow-up If2da01a2: Fix grunt watch
d6e7af8 Adding OO.ui.TitledElement as mixin to label widget
6385af7 MediaWiki theme: Add filled white background to toolbars
837b2f7 Revert "Try to stop user from tabbing outside of open dialog box"

Change-Id: I63d51311f73d1295a2a35ebadf7d9ac835dec5c7