Add group assigment to issues.

Signed-off-by: Martin Abente Lahaye <martin.abente.lahaye@gmail.com>
Update README

Add groups support to column description.

Signed-off-by: Martin Abente Lahaye <martin.abente.lahaye@gmail.com>
Release 0.1.7

Signed-off-by: Martin Abente Lahaye <martin.abente.lahaye@gmail.com>