Set up continuous integration and publish docs for nhlib

[Lars Butler]

The nhlib repo (https://github.com/gem/nhlib) is now open. We should add a configuration to ci.openquake.org to run automated builds.

Also, we should generate and publish source code docs after successful builds to docs.openquake.org (as we are doing with oq-engine).

[Lars Butler (lars-butler)]

There's no documentation yet to speak of, so we can't really publish anything.

We can setup the CI for testing, but in order to close out this issue we need to publish the docs.