Updated the developer README with a few notes about the git conversion.
Updated the developer README with a few notes about the git conversion.

Signed-off-by: Ken Hornstein <0185733cff6721f90d8f6a9f8d893ddac4ec6cf6@pobox.com>

dscho/nmh,mcr/nmh,dscho/nmh,dscho/nmh,mcr/nmh,dscho/nmh