Support SauceLabs Test Running

Problem
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Need a way to run init tests cross-browser during CI.

Solution
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- Create `karma:sauce` task.
- Update `karma-*` dependency to use `karma-sauce-launcher` plugin.
- Create `grunt ci` task that uses the `karma:sauce` task.
- Remove unused BrowserStack support.
- Clean up pesky `jasmine:integration` task wiring.
- Update `README.md`

Unit Tests
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- Modified

How To +10/QA
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- Travis CI should pass.
- Consuming repo should have successful build: https://travis-ci.org/WebFilings/wf-common/builds/32278266

@lancefisher-wf @robbecker-wf @patkujawa-wf @georgelesica-wf @tomconnell-wf @todbachman-wf