jenv: update README

plugins/jenv/README.md

-# jenv oh-my-zsh plugin
+# jenv plugin
 
-[jenv](http://www.jenv.be/) is a Java version manager similiar to [rbenv](http://rbenv.org/) and [pyenv]|(https://github.com/yyuu/pyenv).  This plugin initializes jenv and adds provides the jenv_prompt_info function to add Java version information to prompts.
+[jenv](https://www.jenv.be/) is a Java version manager similiar to [rbenv](https://github.com/rbenv/rbenv)
+and [pyenv]|(https://github.com/yyuu/pyenv).
+
+This plugin initializes jenv and adds provides the jenv_prompt_info function to add Java
+version information to prompts.
+
+To use, add `jenv` to your plugins array in your zshrc file:
+
+```zsh
+plugins=(... jenv)
+```