When deleting a page that isn't in view, pan there first, then delete it

[toolness]

This issue has been migrated from mozilla/webmaker-android#1763.

It was originally written by flukeout on Sun May 10 2015 and had the following description:

Right now you can select a tile, pan somewhere else, and delete the selected page without seeing it. I think it would be good to pan back to the page you're acting on to reinforce what just happened.