Add gemspec for bosh agent.
Add gemspec for bosh agent.

This does not replace the Gemfile yet due to some remaining issues with
dependency selection by platform. I plan to use it to build the gem and
vendor it in the micro repo.

Change-Id: I05f72e0063df20dbd6e88ba9dad5fa2c10b5c836

barthy1/bosh,barthy1/bosh,barthy1/bosh,barthy1/bosh