Fix and style the "Changes suppressed" link.

At some point the "Changes suppressed. Click to show" link stopped behaving as expected, so this fixes it.

I also thought it looked bad:

![Screen_Shot_2015-07-23_at_4.06.49_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/0a1552e4edb659f065bd202b93bc61ef/Screen_Shot_2015-07-23_at_4.06.49_PM.png)

So I gave it some room to breathe:

![Screen_Shot_2015-07-23_at_4.00.25_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/abc0704e597ed010cade81782ac9099e/Screen_Shot_2015-07-23_at_4.00.25_PM.png)


See merge request !1038