Godeps: update tsuru
tsuru: change key-add and key-remove

Now they take the name of the key as well as the path of the key file
(key-add only). Next step is adding key-list, and extending key-add to
support reading the key from stdin.

Related to #189.
tsuru: extdend key-add so it support reading keys from stdin

Related to tsuru/tsuru#189.