Updates to Clojure 1.5.0 final

`lein koan test` passes. I'm not sure if there are other tests to worry about before upgrading to Clojure 1.5.

```
[skim@master][~/lolcat/clj/clojure-koans] lein koan test
Retrieving org/clojure/clojure/1.5.0/clojure-1.5.0.pom from central
Retrieving koan-engine/koan-engine/0.1.3/koan-engine-0.1.3.pom from clojars
Retrieving org/clojure/clojure/1.5.0/clojure-1.5.0.jar from central
Retrieving koan-engine/koan-engine/0.1.3/koan-engine-0.1.3.jar from clojars

Tests all fail before the answers are filled in.

All tests pass after the answers are filled in.
```