Add foreman back to Gemfile

[LiAh Sheep]

$ rake cnpaas:start
/Users/LiAhSheep/.rvm/gems/ruby-2.1.2@global/gems/bundler-1.6.3/lib/bundler/rubygems_integration.rb:252:in `block in replace_gem': foreman is not part of the bundle. Add it to Gemfile. (Gem::LoadError)
    from /Users/LiAhSheep/.rvm/gems/ruby-2.1.2/bin/foreman:22:in `<main>'
    from /Users/LiAhSheep/.rvm/gems/ruby-2.1.2/bin/ruby_executable_hooks:15:in `eval'
    from /Users/LiAhSheep/.rvm/gems/ruby-2.1.2/bin/ruby_executable_hooks:15:in `<main>'

[LiAh Sheep]

fixed as of pull request #53