Moved null-default map creation into its own suite and made that a before in a suite that operates on the null-default map so that each of those tests can be run independently.
Updated interestingCells test to be less brittle.
- Added hashmap-based implementation of cellmap.
- Added support for --use-hashmap switch in cellmaptest.js.
- Updated tests to be less brittle.
Replaced _.cloneDeep in createNullDataCell.
Switched to hashcellmap as the default implementation.
Added check for module.exports so that it works in browser.