Move vSphere systems tests out of rake and into Ruby
AWS Bat Deployment Manifest takes stemcell version, instead of object

 * internal refactor of AWS and vSphere runners
Move 'ensure teardown' logic out of rake task and into Runners
Clean up requires, move fakefs require into spec_helper

 * specs must still call 'include FakeFS::SpecHelpers' to activate fakefs
 * use full modules in specs
 * specs only require class under test
Add class to encapsulate deployments-aws repo access
Bosh::Dev::Aws::Receipts ensures the repository it needs exists
Move AwsDeploymentsRepository under Bosh::Dev::Aws and rename
Refactor Bosh::Dev::Bat::Shell

* Split up the monolithic `#run` method into more sensible logical
  blocks.
* Simplify each of those blocks.
* Add a test for the expected behavior when we ask for a tail of more
  lines than are in the output.