Feature: shimmer

[jasonewall]

Adds a dotfiles feature for installing the shimmer tool

To install - from your own my-dotfiles branch:

git merge feature/shimmer

Add shimmer to your feature list in https://github.com/jasonewall/dotfiles/blob/my-dotfiles/dotfiles/dotfiles

e.g.

for feature in shimmer my-other-feature; do
   ...
done