content suggestions for README

[mmckerns]

*) What you have on the cmi_exchange README is a good start, but still doesn't really tell me what CMI_exchange is. You should always assume that someone comes to every page directly through a google search, so make it have a singular focus… and explain the one thing that you want that page to do for you up front. Why should I clone and start running scripts? Are people supposed to upload stuff and share here? is that what "community developed" means? How about: this is a collection of useful cookbook scripts for solving complex modeling problems using the diffpy/CMI tool-suite. If you need help building your first example, this is a good place to start. It's also a good place to contribute. The goal might be something like this page: http://matplotlib.org/gallery.html (less pretty, most likely… but in spirit).

*) cmi_plugins… contains ipython plugins and functions for what purpose?

*) cmi_cripts… (typo) and again, why should I care? If you reference diffpy-CMI, you should link back to it.