Removing Gem installs

I don't think these gem installs do anything considering we use appbundler, which is just copying from the source directory (see https://github.com/opscode/omnibus/blob/cf4b18fb94f724956b28592cde0890fe42cf6fbe/lib/omnibus/builder.rb#L289).
Also pointing to chef app.
Thoughts?
cc @danielsdeleo @opscode/client-engineers

Note: This builds on windows, running through CI now
I think we will need to run this under `bundle exec` from the source directory. I'm not perfectly sure how to change the `cwd` when launching a service.