Added better typescript support.

Added React 16 as peer dependency.

Add Scatter to Typescript definition.

Removed find polyfill in favor of lodash find.

Legend can be set now through both the options prop as well as the legend prop

Added Legend customization support #158
Added polyfill for find. #109

Re-added canvas as a dev dependancy.

Full list at #130

Replace Object.assign in favour of spread. Resolves issues for IE not supporting Object.assign