Fix incorrect title when changing diff to another file
Fix incorrect title when changing diff to another file

Previously, we emitted a `did-change-title` event and passed in the new
title as an argument. However, Atom doesn't use this argument, and
directly calls `getTitle` on the pane item. Since we were emitting in
`componentWillReceiveProps`, which happens *before* the next render, the
title was one item behind.

atom/github,atom/github,atom/github