Add Commits tab title like Branches, Tags, Compare [UI]

to make them more uniform.

After: removed `compare` from breadcrubs, added Compare h3 header:

![screenshot from 2014-11-14 09 58 48 after](https://cloud.githubusercontent.com/assets/1429315/5043395/19a4a2ae-6be5-11e4-9b85-154f43d210cb.png)

Before:

![screenshot from 2014-11-14 09 58 57 before](https://cloud.githubusercontent.com/assets/1429315/5043398/20f24d54-6be5-11e4-908c-9377218b8580.png)

The goal is to make it more uniform with the other tabs like Branches:

![screenshot from 2014-11-14 09 59 08 uniform](https://cloud.githubusercontent.com/assets/1429315/5043419/53e2f01a-6be5-11e4-8f87-fedf78860c3c.png)