Resolve "Runner list doesn't work"

This merge request fix a bug and add two minor improvements.

It fixes #203 (closed) that wasn't saving the user ID ad the runner creation.

The two improvements

The first improvement is the adding of the runner ID in the Django admin. It lets a superuser to access at any time a runner data. This wasn't possible before if the user created a runner without specifying a hostname.

Second improvement is the URL redirection at runner creation. Before, the behaviour was to redirect the user to the his runner list. Now he's redirected to runner (just) created page. This let the user to copy the docker command directly and enter it on the runner to declare it on A||go.