grunt update and support for custom messages with custom patterns

grunt is now > 0.4
phantomJS added to package.json

but more important:

_.extend(Backbone.Validation.patterns, {
  myPattern: {
    pattern : /my-pattern/,
    msg : 'attr: {0} didn't match pattern: {1}'
  }
});

All tests pass, as well as a few new ones. README.md updated.