Titleize blob action buttons.

As supported by dosire at: https://github.com/gitlabhq/gitlabhq/issues/7789#issuecomment-57126623

I think it looks better.

After:

![screenshot from 2014-09-29 23 10 14 upcase actions](https://cloud.githubusercontent.com/assets/1429315/4449602/7945114e-481d-11e4-8a54-9b0e783e6956.png)

Before:

![screenshot from 2014-09-29 23 12 03 titleize blob action before](https://cloud.githubusercontent.com/assets/1429315/4449605/80dcd586-481d-11e4-8975-88ee6af733aa.png)

In particular, those buttons being lower case already conflicts with the analogous buttons on merge request diffs. 
Prefer single-quoted strings when you don't need string interpolation or special symbols.