[texdoc] Development moved to github

[Manuel Pégourié-Gonnard]

Hi all,

Just to announce that I moved texdoc's development code hosting to
github (sorry, Karl). Updated instructions to download and run the
development version are available at:

http://tug.org/texdoc/dev/

Btw, I reworked the code quite a lot recently, so I'd be grateful if you
could give it some testing before I upload to TeX Live.

Thanks,
Manuel.