Add some space on the left of the bare logo sidebar

Under non-wide circumstances, the blog's sidebar would get squished right up to the side.

Before:

![before](https://cloud.githubusercontent.com/assets/4592/5210846/56aab4ce-75a2-11e4-9572-69df6d10be09.png)

After:

![after](https://cloud.githubusercontent.com/assets/4592/5210848/58fe55be-75a2-11e4-9f29-4fa7a76906b2.png)

Fixes #311.