SD Website Design Entry & Image-Grid Edits

- Re-added the entry for the design of the SD website (from my old portfolio)
- Edited the image-grid code so the number of columns can be specified (if not, it defaults to 4 on desktop)(set to 1 on mobile)
- Edited the image-grid invocations in the entries that made use of it
- Edited some base styling (Quartz puts an embedded image in a paragraph tag)

Author: joshwingreene