Add label collection methods, clean up API a bit#19

Merged

travisbrown-stripe merged 2 commits intostripe:masterfrom travisbrown:topic/tree-ops

Jun 6, 2017

+53-29

Commits on Jun 1, 2017

Add methods for collecting labels

jhoon-stripe
authored and
travisbrown-stripe
committed
More consistent / general API
travisbrown-stripe
committed