[JS Code Hints] Html script hinting

Implement codehints and jump-to-def for javascript inside <script> tags in a .html file.

To support html hinting, the code strips out the non-javascript parts of the html file.  We replace them with whitespace so that the offset and cursor positions don't have to be translated.  Then the javascript-only contents are sent to tern for processing so that the html tags don't confuse the js parser tern uses.

Also adds a few units tests to make sure html hinting continues to work.