add convenient entry point for cwltool (#66)

* add convenient entry point for cwltool
* clarify that this is not recommended

Author: mr-c

cwltool.py

@@ -0,0 +1,12 @@
+#!/usr/bin/env python
+"""Convienance entry point for cwltool.
+
+This can be used instead of the recommended method of `./setup.py install`
+or `./setup.py develop` and then using the generated `cwltool` executable.
+"""
+
+import sys
+from cwltool import main
+
+if __name__ == "__main__":
+    sys.exit(main.main(sys.argv[1:]))