Improve module readmes

[allanaaa]

This is not an issue on this repository, just a to-do item for me. The module readmes are displayed on the website's module directory, but some have very little information about why a user would want to install it. Readmes also contain lots of developer info that can show up quite high on the page and perhaps put off prospective users.

So:
For each module, add more general info about module function and features (and requirements) to each readme. This includes a fix for PR #145, which is developer info that should be in the readme.

Note to self that Readme links need to be markdown-formatted. They appear clickable in the readmes on github but do not render as links on our website.