delete server without tests
BoundLog eq implemented

useful when testing different mock_log objects bound with same args
FakeSupervisor for easier testing - inspired from @radix
working delete server implementation

- delete endpoint is now "DELETE ../groupId/servers/serverId" instead of
"POST ../groupId/delete_server".
- Not implementing GET on ../servers/ and servers/serverId
- moved remove_server_from_group from controller to supervisor
- tests added for rest and supervisor changes
fix tests
using BoundLog matcher
Removed BoundLog.eq and using its matcher
Restoring job test code
added description while displaying matcher
Extracting bool args in separate func - thanks @lvh

- Adjusted rest/group tests accordingly
- s/ServersBelowMinError/CannotDeleteServerBelowMinError for clarity -
thanks @cyli and @MariaAbrahms
min check on active + pending - thanks @cyli
better checks in tests - thanks @cyli
Revert "added description while displaying matcher" - per @cyli

This reverts commit 91e14baec61fd4d78f71002c4271fd0aa11c0374.
Merge pull request #633 from rackerlabs/as-265-group-del-server

AS-265: delete server (review)