fix OrderedMap.entryAt where entry has falsy value
Comment clean-up
Merge branch 'master' into develop
Merge remote-tracking branch 'revelytix/revelytix' into develop

Conflicts:
	test/flatland/ordered/set_test.clj
Remove a silly println I accidentally left in.
Version 1.5.1, with a fix for falsey values in maps
Merge release branch for 1.5.1