Add a check to the build logic to see if node is present

The ClojureScript tests rely on node being present, if it's not there then they
will fail in non-obvious ways. To provide quick feedback we do a check first
before starting the tests.

Makefile

@@ -1,4 +1,4 @@
-.PHONY: test-clj test-cljs eastwood cljfmt cloverage install smoketest release deploy clean
+.PHONY: test-clj test-cljs eastwood cljfmt cloverage install smoketest release deploy clean check_node
 
 VERSION ?= 1.9
 export CLOVERAGE_VERSION = 1.0.13
@@ -53,6 +53,9 @@ smoketest: install
         lein with-profile +$(VERSION) uberjar && \
         java -jar target/smoketest-0.1.0-SNAPSHOT-standalone.jar
 
+check_node:
+	which node
+
 # When releasing, the BUMP variable controls which field in the
 # version string will be incremented in the *next* snapshot
 # version. Typically this is either "major", "minor", or "patch".