JRuby: update and lock version of RubyGems
JRuby: update and lock version of RubyGems

JRuby 1.7.4 do not have RubyGems 1.8.25 with it, so an update is
required.

ruby-concurrency/rake-compiler-dev-box,tjschuck/rake-compiler-dev-box,ruby-concurrency/rake-compiler-dev-box,flavorjones/rake-compiler-dev-box,ruby-concurrency/rake-compiler-dev-box,copiousfreetime/rake-compiler-dev-box,tjschuck/rake-compiler-dev-box,flavorjones/rake-compiler-dev-box,tjschuck/rake-compiler-dev-box,flavorjones/rake-compiler-dev-box,copiousfreetime/rake-compiler-dev-box,copiousfreetime/rake-compiler-dev-box,ruby-concurrency/rake-compiler-dev-box,tjschuck/rake-compiler-dev-box,copiousfreetime/rake-compiler-dev-box,flavorjones/rake-compiler-dev-box