Fix header logo position

logo position was wonky between 30em and 40em screen sizes
![header-logo](https://cloud.githubusercontent.com/assets/5376785/4122718/65c739b4-32c7-11e4-9534-40b46a946483.png)

Also, it seems goofy to have the source scss files and the resulting CodeKit-generated css files all in source control. I guess there weren't any good Sass packages for Meteor back when Sacha first wrote Telescope? Since this was such a small change, I just manually edited both the source _header.scss and resulting screen.css files. Also, I don't have CodeKit (running Linux here), and I didn't want to regenerate the css with a different Sass preprocessor and introduce a bunch of trivial changes.

Cheers!
Ben