Pipeline as gems

@mattgillooly @kbarrette 

Adds a rake task that will package the pipeline with a gemspec as a gem and upload the deps to s3:

    Pipely::Tasks::UploadPipelineAsGem.new do |t|
      t.bucket_name = 'the_bucket'
      t.s3_steps_path = 'steps'
      t.s3_gems_path = 'steps/gems'
    end