Add class_mappings kwarg to Salt adapter functions

Closes: https://github.com/madduck/reclass/issues/14
Signed-off-by: martin f. krafft <madduck@madduck.net>
add configfile lookup todo

Signed-off-by: martin f. krafft <madduck@madduck.net>
Update Salt adapter docs wrt configuration file

Signed-off-by: martin f. krafft <madduck@madduck.net>
Prepare reclass 1.2.1

Signed-off-by: martin f. krafft <madduck@madduck.net>