Add Fedora installation instructions to README
Add Fedora installation instructions to README

References the `seeitcoming/rcm` COPR.

Closes #156.

Frost/rcm,Frost/rcm,TheLinuxKitten/rcm,thoughtbot/rcm,TheLinuxKitten/rcm,thoughtbot/rcm,TheLinuxKitten/rcm,Frost/rcm,thoughtbot/rcm,Frost/rcm,TheLinuxKitten/rcm