Added 'binVersion' option to specify against which version to test - solves an issue on Ubuntu

Hi,
On Ubuntu my php reports version '5.5.9-1ubuntu4.4'.
This fails the built-in PHP version check '>=5.4', because semver believes '1ubunbu4.4' is a pre-release tag, and pre-release tags do not match version range (unless they're explicitly listed, see https://github.com/npm/node-semver/pull/99#issuecomment-55044058).
So grunt-php aborts.

To solve it I added an option to specify the version to check against, and I set it to '*' (which matches), but it could also be used to ensure PHP>=5.5, if 
Default is still >=5.4, so it is fully backward-compatible.