Associate .dtm and .edn files with Clojure mode

.dtm is typically used for Datomic schemas and .edn is the
extension of Extensible Data Notation(EDN) files. Both are
essentially Clojure code.
Release clojure-mode 2.1.0.
Release clojure-test-mode 2.1.0.
Merge pull request #134 from bbatsov/dtm-edn

Associate .dtm and .edn files with Clojure mode.