(#37) floaty snapshot warns users about snapshots pending

Vmpooler works by generating a snapshot sha and queueing
the host for taking a snapshot. Depending on the load of
vmpooler, this could take quite a while to complete
making it a little confusing to users trying to use that
snapshot name right away. This commit adds a warning to
the snapshot command about taking snapshots.

lib/vmfloaty.rb

@@ -308,6 +308,7 @@ class Vmfloaty
           exit 1
         end
 
+        puts "Snapshot pending. Use `floaty query host` to determine when snapshot is valid."
         pp snapshot_req
       end
     end