Link to a list of distros instead of one specific distro

Use Repology as the list source, since it is an open source service
and monitors lots of different distros with git-imerge packages.

Fixes: commit f9834c4
Fixes: commit d9a654c
Suggested-by: Paul Wise <pabs3@bonedaddy.net>

Author: waldyrious

README.md

@@ -40,14 +40,13 @@ Bash completion requires Git's completion being available.
 
     $ pip install git-imerge
 
-
 or using `setup.py` if you have downloaded the source package locally:
 
     $ python setup.py install
 
-If you prefer, you can use [Homebrew](https://brew.sh) to install `git-imerge`:
-
-    $ brew install git-imerge
+`git-imerge` is also available to install from
+[package managers](https://repology.org/project/git-imerge/versions)
+on several platforms.
 
 ## Instructions