When using certain html-comments, can.view.Scanner does not recognize them correctly

When using some html-comments (namely all comments, that don’t have a `space`/`tab`/`newline` after the starting `<!—`), can.view.Scanner incorrectly recognize them as tags instead of comments and therefore tries to bind them (which breaks other bindings).

This pull request contains a breaking test for the problem as well as a proposed fix.
**Note:** The fix **will** have a negative impact on overall-performance, though I find it too small to measure how much exactly (I just ran the mustache-tests with and without the fix, didn't make a difference that could not have been cause by normal variation).