Indentation and phrasing around export plugin.

Inspired by https://github.com/gcuisinier/jenv/pull/154

It has conflicts now so it was faster this way.

Forgot to mention previous commit was inspired by
https://github.com/gcuisinier/jenv/pull/164

Thanks @johnjohndoe and @fmassart!

README.md

@@ -251,10 +251,11 @@ Let's say you want Maven to use the JDK activated with Jenv, not the default `JA
 Note: The enable-plugin functionality is system wide not local to the shell, or temporary - you only need to do each one once.
 
 ### Export plugin
-Another one usefull plugin is the "export", that expose JAVA_HOME automatically :
+Another one useful plugin is the "export" plugin, that exposes `JAVA_HOME` automatically:
 
     $ jenv enable-plugin export
-      You may restart your session to activate jenv export plugin echo export plugin activated
+      
+You may need to restart your session to activate it.
 
 ## Development