Allow whitespace around commas in point parsing

Per the SVG spec:

http://www.w3.org/TR/SVG/shapes.html#PointsBNF
Add test for whitespace between commas
Simplify point parsing logic

The SVG spec basically allows delimiting numbers and pairs of numbers
with either whitespace or commas, so convert all commas to whitespace,
split on whitespace and remove the `asPairs` logic
Merge pull request #1478 from paulkaplan/fix-point-parsing

Allow whitespace around commas in point parsing