Unfortunately, following their installation instructions may get you to where I was: Nowhere Land. I kept getting these wonderful error messages anytime I would create a new project:
fatal: remote error: Could not find Repository thoughtbot/suspenders-gem
From the code, it appears the trout file was trying to checkout from their old repository. Their latest code on master seems to be the best place for updates, so a quick fix was to just build the gem from there (code found in the Rakefile):
git clone git://github.com/thoughtbot/suspenders.git
mkdir -p pkg
gem build suspenders.gemspec
mv suspenders-.gem pkg
gem install suspenders-.gem
I use RVM (as you should too), and before I performed this I switched to my firstname.lastname@example.org gem set that I use in the directory that I start in for all my projects. Something you may want to consider as well.
Booom! Suspenders in full force! Enjoy.