OpenStack: Add the ability to use a service token

Service tokens can be used directly without pre-authentication. While
it's possible to use service tokens without this change, it is not
very obvious. This change makes the use of service tokens easier.
Add requests for managing keypairs and floating IPs
Add list_hypervisors request
Less confusing authentication

As is, Aviator::Session#authenticate retuns nil (falsey) on success.
ignore vim swap files
Implement IdentityService#get_user request
Relax runtime dependency requirements

It's never a good idea for a gem to have strict dependencies. A
problem with this though is that we will have to be diligent with
every new release of dependencies. There's no surefire way to prevent
breakage but relying on automated tests and the CI helps.

As part of this requirements relaxation, a change was done on the
VCR setup script such that it doesn't care what version of Faraday
is used.
Catch invalid provider and service names

This changes ensures that the CLI tool `aviator describe` does not
display a stacktrace when an invalid provider is given. The change
also includes further checks for when requests are not found for
a given service.
Bump version to 0.0.9
Fix version dependencies