Reorganize the documentation

Will close issue #257 and #273 
The problem is that without the version (until that Composer PR above is merged, might be soon?) in the `require` command, a user is prompted to enter a version. But, Composer doesn't really help them out by telling them what versions are available, etc. So, we've kind of lost them: a beginner won't really know what to enter here.

I would like to see the `~0.9.0` in the command here, then remove it later when that Composer feature has been merged.