Have OrdinalScale default to "bands" mode.

"Points" mode isn't used as often.
Merge pull request #439 from palantir/ordinal-bands-default

Have OrdinalScale default to "bands" mode.
Split utils.ts into many files
Merge pull request #442 from palantir/split-utils

Split utils.ts into many files
Merge remote-tracking branch 'origin/master'

Conflicts:
	src/core/renderer.ts