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.
Merge pull request #134 from bbatsov/dtm-edn

Associate .dtm and .edn files with Clojure mode.
Indent clojure.test/are like other binding forms

; Without patch:

(are [foo]
     bar
     baz)

; With patch:

(are [foo]
  bar
  baz)
Merge pull request #156 from qerub/master

Indent clojure.test/are like other binding forms