Non xhtml namespaceuri

[TheMarksman]

This PR implements the suggested fix for #4, by letting a user set an explicit xmlns on a tag.

This also adds the minimal possible Travis-CI integration.

Definitely interested in feedback!

[enjalot]

Thanks for the contribution! This being a workaround, we want to think a little harder on the right API. It is a little onerous to ask the user to specify the svg namespace in a partial. A more user-friendly workaround could be specifying that a partial is specifically an svg partial (we don't see much use in having a partial that is both svg and html, might as well keep them separate).

We also want to look into properly fixing this so that users dont need to be concerned with the namespace of their partials.

Could you put the Travis fix in a separate pull request so we can go ahead and merge that in?