chore(travis): use npm cache
revert: test(ngModelOptions): ensure input has focus in e2e tests

This reverts commit 8d38ec38921bf887189eb31b07855ca987beff47.
The protractor tests for ng-model-options were failing locally on Chrome
for me but this commit breaks the tests on Firefox.
chore(travis-build): don't re-package when testing docs

Since .travis is already running `grunt package` in the `before_script`
block there is no need to run it again when testing the docs.
chore(travis): disable captureTimeout

All of the recent failures were caused by too much load on SL, not
an actual problem.

I think a proper solution will be:
https://github.com/karma-runner/karma-sauce-launcher/issues/37
WIP: time npm install on Travis

Wanna see if it's any better now that we use the cache.
WIP: measure npm install without cache (same SHA as with cache)