feat(networks): Reddit submission to share panel.

This is an incomplete feature. I have only outlined how to get to the
right url, given the user leaves the options set to the defaults. I
still have a few outlying problems that I would appreciate help with:

 1. Styling the reddit button. I think a dark blue background and an
    orange or white snoo would work fine.

 2. Including a reddit icon, which isn't available in the entypo
    library, but is available in the font-awesome library.