Add new feature to load custom rules

[sergicontre]

The objective would be to include using the parameter 'modules' , new modules with custom rules. For example, performance custom rules , or specific polymer applications that the developer needs to incorporate.

Rule: detect bad use of addEventListener instead of this.listen. Rule: not remove listen in components. etc...

Example: polylint my-component.html --modules /lib/performance-rules.js

[googlebot]

Thanks for your pull request. It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

:memo: Please visit https://cla.developers.google.com/ to sign.

Once you've signed, please reply here (e.g. I signed it!) and we'll verify. Thanks.

---

• If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address. Check your existing CLA data and verify that your email is set on your git commits.
• If you signed the CLA as a corporation, please let us know the company's name.

[sergicontre]

I signed it!

[googlebot]

CLAs look good, thanks!