LGTM
https://codereview.appspot.com/559870043/diff/553910043/lily/include/box.hh File lily/include/box.hh (right): https://codereview.appspot.com/559870043/diff/553910043/lily/include/box.hh#newcode38 lily/include/box.hh:38: /// smallest box enclosing `this` and `b` Why '///' instead of '//'? https://codereview.appspot.com/559870043/
