Add multiple sources when merging ruby dependencies

[Stephenitis]

According to the Source Priority section in the Gemfile manpage sources are searched from last entered to first entered.The following does not work in a Gemfile uploaded to IronWorker.

source 'https://rubygems.org'
source 'http://our.own.gem.repo.com/the/path/to/it'

gem 'gemfromrubygems'
gem 'gemfromourrepo'

inside .worker it would also be nice to set custom source and misc options

gem 'gemfromourrepo', source: 'http://our.own.gem.repo.com/the/path/to/it'