Use new cloud-client instance filtering in ey servers

Adds new filtering options to ey servers to return just
the instances you need for scripting.
Merge pull request #182 from engineyard/servers

Use new cloud-client instance filtering in ey servers
Next version will be 3.0.0

Includes non-backwards-compatible change to required ruby version
A little refactor to ey ssh
Add ey scp command to send files to some/all servers