Renaming hydra.rb -> hydra6.rb

Prior to this change, the `require 'hydra'` declaration did not load the
hydra gem's lib/hydra.rb but instead loaded hydra-head/lib/hydra.rb.
Pegging to patch version of gems
Bumping version to 6.0.0.rc4
Consolidating install instructions via generator
Bumping version to 6.0.0.rc5
Merge branch 'master' of github.com:projecthydra/hydra