Several tiny fixes, including #100

These seem straightforward, but if you don't want all of this, I can break it into separate PRs. Let me know.

Incidentally, the cause of #100 seems related to the invoked (two-arg) version of `last-day-of-the-month` having primitive type-hints (i.e., it's a `clojure.lang.IFn$LLO`). I guess the compiler won't accept a type-hint on an invokePrim expression. I can't find an open Clojure bug about it, but there is this resolved one in the neighborhood: http://dev.clojure.org/jira/browse/CLJ-850.