Add support for URL configurations

This pull req adds support for an optional proctor.test.matrix.url config property, which will pull the matrix info from an external server. 

I was unable to build with the specified version of the bitwalker UserAgentUtils -- the groupId wouldn't resolve, and 1.13 wasn't available under the eu.bitwalker groupId.  Updating to the current version was the only way to resolve the dependency issues.  Per https://github.com/HaraldWalker/user-agent-utils, this also adds:
* IOS8 support added
* added Opera Coast as new mobile browser
* more Chrome and Firefox versions added, including future releases (up to Firefox 40 and Chrome 40)
* added 3 Opera versions
* performance improvements