Don't run as root, don't run plugins, and bonus spec file

First, sorry for three commits in one PR.  I fail at github.

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It's a bad idea to run wp-cli as root.  This is a bit heavy handed.  Maybe needs a config option?  Looking for feedback.

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Also, bad plugins can break wp-cli altogether.  Example:
http://plugins.svn.wordpress.org/redirect/tags/0.8/redirect.php

The fix is to only load specified plugins.  For most functions, you don't need plugins.  For when you do, just run with "--enable-plugins=plugin1,plugin2" and it works with globbing, too so "--enable-plugins=*" works.

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And finally ... I use a variant of this makefile/spec combo to build a wp-cli rpm for easy deployment.  Hope it's useful!

(Again sorry for the three commits in one PR)