Move the tests for HTML comment.

These are not only for tolerant mode, place them in the Comment category.

https://code.google.com/p/esprima/issues/detail?id=451
Support --> HTML comment.

From http://javascript.spec.whatwg.org/#comment-syntax:

  --> at the start of a line, optionally preceded by whitespace or
  MultiLineComments, must be treated as a SingleLineComment
  — equivalent to //.

https://code.google.com/p/esprima/issues/detail?id=451