Changing repo after first deploy leads to inconsistency

Hello,

I generated a couple of times GH pages using a config. I therefore changed the `repo` option to another repository.

The cloning into `.grunt/grunt-gh-pages` indicated the proper repo URI **but** the push was still executed towards the former repo origin.

I had to delete the `.grunt` folder and re-run the `gh-pages` task to deploy to the new `repo` value.