Minor doc/formatting tweaks to saucelabs support
First mostly-working version of browserstack integration
Pull browserstack tunnel jar downloading into a separate task
Fix hang on browserstack tunnel startup
Support default ports for browserstack tunnel application urls
Update browserstack integration documentation to use platforms that are actually supported
Update default download location of BrowserStackTunnel.jar
De-dup cloud browser testing integrations.

Merge saucelabs and browserstack manual chapters, browser spec, common driver factory and tunnel logic, tasks
Address issue from review

* Fix a couple doc errors
* Change `geb.sauce.browser` to `geb.saucelabs.browser`
* Change `allSauceTests` to `allSauceLabsTests`
GEB-302 Add some tests that guard performance by verifying which WebDriver commands are executed
Merge branch 'feature/browserstack' of git://github.com/davidmc24/geb

Conflicts:
	doc/manual/src/chapters/140-project.md
Whitespace
* Use BrowserStack to run cross browser tests
* Support running multiple tunnels to BrowserStack