- Mention github instead of wiki
- Add markdown as allowed format
- Fix some weirdnesses such as "A BIP editor must subscribe to the
gmaxwell@gmail.com list.". Remove the repetition and create a new section
which lists the BIP editors (currently only gmaxwell).
- Prefer discussion on mailing list to forum

This is just a cleanup and change for the github move. I have not changed
the process to jgarzik's new proposed process (
http://sourceforge.net/mailarchive/forum.php?thread_name=CAAS2fgROsymXnXTrfLTLTQ%3DEDwaAFu%2BxrrD4Q-Gye5XWze7vFw%40mail.gmail.com&forum_name=bitcoin-development),
this can be done in a later separate change.

See pull request here:
https://github.com/bitcoin/bips/pull/1

Regards,
Wladimir