Added grunt config files

Signed-off-by: Jesús Merino Parra <jmmerino@gmail.com>
Activate _depth property and add conditional to deactivate color_target property.

Signed-off-by: Jesús Merino Parra <jmmerino@gmail.com>
Merge pull request #31 from jmmerino/master

I have activated _depth property and I have added conditional to deactivate color_target property also.