Pulled HttpUnit out of OneBrowserPerTest/Suite.
Renamed Browser to BrowserDriver.
Renamed FirefoxBrowser to FirefoxDriver, but realized this clashes with names
in Selenium itself, so next step will be to change it back but rename Driver to
BrowserDriver.
Renamed HttpUnit/FirefoxDriver back to HttpUnit/FirefoxBrowser and ignored out the HttpUnit test
that is failing on my Mac.
Added HttpUnit NoArg.