feat(build): Adding htmllint Grunt task

This isn't linked to any `default` or `lint` Grunt task since it adds 15-20s per build, but it's nice to keep around since it may catch some HTML markup issues in the future.

```sh
$ grunt htmllint

Running "htmllint:all" (htmllint) task
>> 697 files lint free.

Done, without errors.


Execution Time (2014-07-24 19:11:53 UTC)
loading tasks   1.7s  ▇▇▇▇▇ 10%
htmllint:all   15.3s  ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 90%
Total 17s
```
this PR is a bit old and I'm not exactly remembering what a lot of these blacklists were for.
I vaguely recall something about **marked** module converting \<H[1-6]\> tags into headings and giving them an `id` automatically. Sounds harmless, but for localized languages with "funny characters" I think it was just setting the `id` field to `id="-"` or something silly. Let me rebase this and tweak these `ignore[]` rules and see if I can find examples of where/why.