[DRE-maint] ruby-gruff is marked for autoremoval from testing

[Debian testing autoremoval watch]

ruby-gruff 0.6.0-1 is marked for autoremoval from testing on 2016-12-13

It is affected by these RC bugs:
841133: ruby-gruff: FTBFS: Tests hang after segmentation fault

It (build-)depends on packages with these RC bugs:
591419: ruby-rmagick: librmagick-ruby should not be installable with imagemagick