Switch to whacko/parse5

Use parse5 automatic head/body insertion

Depend on parse5 to make proper head and body tags, use those to insert correctly into head and body of master document

Mostly removes need for  <div hidden></div> trick, except for the the final concatenation into main document body.

Fixes #73 html5 compatible parser?
Fixes #61 Vulcanizer inlines non-head content into head, generates incorrect HTML
Fixes #53 Vulcanize breaks SVG.
Fixes #67 Characters with accents are not properly converted/formated
Don't create a whole document for inlining styles
Keep consistent ordering of import document heads and bodies
Merge pull request #77 from Polymer/use-whacko

Switch to whacko/parse5