create copy of scale so requestedSpace is now pure
close #487
Merge branch 'master' into 487-cat-axis-purity

Conflicts:
	plottable.js
	src/components/categoryAxis.ts
added newline
Merge branch 'master' into 487-cat-axis-purity

Conflicts:
	plottable.js
Merge pull request #615 from palantir/487-cat-axis-purity

create copy of scale so requestedSpace is now pure