Check in the lockfile

This prevents rubocop from automatically using the latest version and breaking the builds.  This also gives people a baseline where they can point at a set of dependencies that passed the build. This is the practice recommended by Bundler: https://bundler.io/guides/faq.html\#using-gemfiles-inside-gems

Author: jcoyne

.gitignore

@@ -5,10 +5,8 @@
 .yardoc
 .rvmrc
 *.log
-Gemfile.lock
 coverage/
 doc/
-gemfiles/*.gemfile.lock
 jetty/
 log/*
 tmp/*