Fill out README.rst with instructions to build docs and pointer to online version. Refs issue #1

Let me know if I should change something. Also, advices are welcome concerning the built of pdf documentation. I still have some strange error after the build, and the result is a pdf file with basically 6 blank pages :( 
This is actually the ones needed. But, texlive-full will bring a huge list of dependencies :( Install texlive alone, and it won't work. I'm actually looking for an alternative. I'll let you know.