This prevents the jenv plugin from messing up the PATH and putting `user/local/bin` back at the front of the PATH, undoing any careful setup done before enabling this plugin.
Initializes jenv and provides the jenv_prompt_info funtion to add
Java version information to prompts. This function is stubbed in
prompt_info_functions script to allow it to be safely called
regardless of whether or not the jenv plugin is loaded.
It also splits detection of the plugin/versions directory and bin directory
to suppport the way Homebrew splits the jenv bin and data directories
Marc Cornellà