adds thanks and lots of adjustments (thanks phil9)

adds manpage installation

surprisingly easily. rules already exist. Plan 9 is love

removes old readme, adds samplerules, adds man-readme

see samplerules for sample configuration. see (rendered) man page for usage info

adds rudimentary plumbto man page

renames Readme.md -> README.md

adds basic readme.

adds MIT license

adds files

this adds mkfile and plumbto.c source code.
The project works already, you need the channel in your plumb rules

	echo plumb to chanselect >> /mnt/plumb/rules

the messages need destination to this channel, as well as the attribute:

	channels=chan1,chan2,chan3

Whenever a message arrives there, the window pops up and you can click the
correct destination channel (these are buttons). The message is altered (the
channels attribute is removed) and delivered.