add support for javadoc

[hanfeisun]

I found this plugin awesome.

Only one things that I think need to be improved may be the support for javadoc

For example:

user> (use 'clojure.java.javadoc) nil user> (javadoc java.net.URL) ; Evaluation aborted. "http://java.sun.com/javase/6/docs/api/java/net/URL.html"

It would be much easier If I can point to java.net.URL, can type in C-c C-d C-j