Update to use ->markTestSkipped()

PHPUnit has in built test skipping, this should be used over @group skip,
as this means that testing commands can be ran from any working directory
rather than from the base php directory.  Unsure as to whether exercism will
actually currently provide the phpunit.xml - but this means there's now no
longer a need to serve files to the root either
Remove (now) spurious annotations from hamming test
Fix up MakeFile so all tests are ran against example
Merge branch 'master' of git://github.com/exercism/xphp into cleanup-skipping
Remove skips + Documentation for skips
Re-add skip for test that requires it
Merge pull request #22 from Mezzle/cleanup-skipping

Cleanup skipping