Add `friends graph --unscaled`

[Jacob Evelyn]

I wonder if it would be neat to be able to do something like friends graph --with Chantal --scaled to see a scaled representation, like:

Apr 2018 |████∙∙∙∙∙∙|
May 2018 |██∙∙∙∙∙∙∙∙|
Jun 2018 |███████∙∙∙|
Jul 2018 |█████████∙|

The idea is that you can more easily see the flows of a relationship over time. It's possible that this should actually be the default, and that --unscaled should be the flag to turn this off.

This could even be used for the friends graph command with no other flags, in which the maximum scaled value is the most activities for any month, and other months scale against that.