Updated BIP-0001 for github move

- 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