ARQ-1537 Support for Safari browser

Basic implementation of Safari BrowserCapabilities.

Works with Safari 5.1.3, System info: os.name: 'Mac OS X', os.arch: 'x86_64', os.version: '10.7.3', java.version: '1.6.0_31'.

SafariDriverTestCase is ignored because SafariDriver cannot access URLs with file: protocol (http://code.google.com/p/selenium/issues/detail?id=3773).