Add external module structure like sphinxcontrib

[heavenshell]

Hi,

Currently rstblog need to put extra module into modules directroy.

For example when I create module like youtube.py, which shows thumbnail in blog, I put it into modules directory manually.

IMHO third party module should not put into rstblog.modules directry.

So I wrote a patch, which can handle external module structure like sphinxcontrib.

Here is a sample config.yml

---
active_modules: [pygments, tags, blog, latex]
extensions: [rstblogcontrib.youtube]
modules:
  pygments:
    style: tango

1. Add extensions list in config.yml.
2. ./run-rstblog build execute rstblogcontrib.youtube.setup().

If you don't need any extensions, delete extensions line, so rstblog would not execute extensions.

Please check it and include.

Regards,