Updates to the clojure examples, including:

* lein-based examples now use the latest mod-lang-clojure and clojure
  versions
* examples that start servers now have completion handlers that print
  exceptions or welcome messages
* the upload client now properly converts the content-length header to
  a string instead of throwing an exception
Merge pull request #15 from tobias/clojure-example-updates

Updates to the clojure examples, including: