Resize the logo to the size it's being used.

This fixes the problem with old browsers that don't support the `background-size` property.
Switch to `row-fluid`.

This fixes issues with older browsers like IE8.
Switch to using an `img` for the logo.

Also fix the navbar elements overlapping in 754px-767px width.
Make the navbar responsive.
Merge pull request #229 from XhmikosR/logo-img

Improve older browsers support