Pin gem-versions?
Otherwise users might run into problems like this:
/usr/lib/ruby/2.3.0/rubygems/specification.rb:2284:in `raise_if_conflicts': Unable to activate activerecord-4.2.6, because activesupport-4.2.5.2 conflicts with activesupport (= 4.2.6) (Gem::ConflictError)