Style changes as recommended by mbostock:
- Various whitespace modifications
- underscore var names -> camel case
- extract point sort comparator to a global function so it’s not constantly initialised each time you hull
- postincrement -> preincrement in for loops
- use single `var i` at top of function rather than constantly redeclaring for each for loop
Refactor isLeft out of clip-extent into trigonometry
Minor whitespace issue