Bump versions, add a namespace, remove record? predicate

- Bumped version of clojure specified to 1.6.0
- Bumped version of backtick to 0.3.1
- Removed `record?` definition as it now exists in clojure 1.6.0
- `src/backtick.clj` => `src/backtick/core.clj` with associated rename in resulting `core.clj`