Refactor the informative messages for set/get threshold commands

Signed-off-by: Radoslav Dimitrov <dimitrovr@vmware.com>

Author: rdimitrov

README.md

@@ -115,12 +115,12 @@ should be distributed to clients for performing initial updates.
 
 #### `tuf set-threshold <role> <threshold>`
 
-Sets the `role` threshold (required number of keys for signing) to
+Sets `role`'s threshold (required number of keys for signing) to
 `threshold`.
 
 #### `tuf get-threshold <role>`
 
-Outputs the `role` threshold (required number of keys for signing).
+Outputs `role`'s threshold (required number of keys for signing).
 
 #### Usage of environment variables
 

cmd/tuf/set_threshold.go

@@ -28,6 +28,6 @@ func cmdSetThreshold(args *docopt.Args, repo *tuf.Repo) error {
 		return err
 	}
 
-	fmt.Println("The treshold for", role, "role is", threshold)
+	fmt.Println("The threshold for", role, "role is now", threshold)
 	return nil
 }

repo.go

@@ -478,7 +478,7 @@ func (r *Repo) RevokeKeyWithExpires(keyRole, id string, expires time.Time) error
 
 	err = r.setMeta("root.json", root)
 	if err == nil {
-		fmt.Println("Revoked", keyRole, "key with ID", id)
+		fmt.Println("Revoked", keyRole, "key with ID", id, "in root metadata")
 	}
 	return err
 }