Remove unnecessary break statement

This doesn't seem to make sense:

    switch (k) {
      case 'complete':
      case 'duration':
      case 'easing':
      case 'bezier':
        continue;
        break
    }

JSHint seems to agree. While working on another pull request, I got this:

    - Boo! *./src/morpheus.js* FAILED JSHint with 1 error:
      (error) line 340: Unreachable 'break' after 'continue'.