Add self-url.
When launching browsers, only test those browsers.

Do not use all agents connected to the Hub, instead use only
the browsers that were launched.
Restart browser API.
Consolidate forEach calls.
Merge branch 'master' into wd-subset
Add Sauce Labs browsers.
Handle end before complete.
Setup Target with UA. New appendTarget method.

No longer infer the UA from passed-in targets.
Ask Target if new Agent is allowed.
Restrict WebDriver batches to launched browsers.
Fix server-side `wd-url` option.
Workaround echoecho & Yogi issue for JSONP tests.

This keeps Yeti's behavior in sync with Yogi, which is
used to develop JSONP tests in YUI.

See: https://github.com/davglass/echoecho/issues/11
Accept "latest" as a WebDriver browser version.
Fix WebDriverCollection unit test.

 - batch property is required in ctor object argument
 - code fix: webdriver should not be a required property
 - agentIds is no longer a property on the WebDriverCollection,
   replace with getAllAgentIds()
Add tests for new WebDriverCollection APIs.
Factory for WebDriverCollection mock creation.
Add test for quit during WebDriver init.

Fix hang when launch callback is never called during
a quit on init.
Merge branch 'wd-subset'