Add RankedTree#94

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fgreen wants to merge 4 commits intomasterfrom

feature/RankedTree

Commits on Mar 23, 2017

Add RankedTree. I didn't end up using this, but it's fairly complete and might be useful later
fgreen
committed

Commits on Apr 7, 2017

Commits on Apr 12, 2017

Merge branch 'master' into feature/RankedTree
o8ruza8o
committed