Show `abbr` site title for larger widths. Close #526.

Show the `abbr` text content on smaller widths where less room is available. When we have the width, swap our text content with title attribute.

`<abbr title="Hixson-Lied College of Fine and Performing Arts">HLCFPA</abbr>`
Use font-sizes to show/hide site title parts.
Merge pull request #527 from smeranda/site-title

Show `abbr` site title for larger widths. Close #526.