Dichotomy 3.0

Whoa, look at that shiny “3”! This version of Dichotomy introduces:

• A “left-handed” layout option that switches the placement of posts and navigation.

• Refined mobile styles, and the option to always turn them on regardless of device.

• Fixes for the “never miss another post” teaser, and code to suppress the whole-page sliding one.

• A rewritten, slightly less pedestrian README.

• Magic fairy dust.