Add "composure" from "https://github.com/erichs/composure@1.3.1"

git-vendor-name: composure
git-vendor-dir: vendor/github.com/erichs/composure
git-vendor-repository: https://github.com/erichs/composure
git-vendor-ref: 1.3.1

vendor/github.com/erichs/composure/test/Makefile

@@ -0,0 +1,18 @@
+
+TARGET = tests
+
+all: $(TARGET)
+
+runtests:
+	./runtests.sh
+
+runshellcheck:
+	./runshellcheck.sh
+
+tests:
+	./wvtestrun $(MAKE) runshellcheck
+
+clean::
+	rm -f *~ t/*~
+	rm -rf composure_test
+