Document proc settings

Hi there...

I've been using this in development for a while and it's working great. I'm planning on putting it into production shortly.

I thought it would be a good idea to document the various settings that control SysV queues. It took me a while to figure out what was going wrong since the error messages are a bit cryptic:

    Invalid argument - Failed sending message to queue (Errno::EINVAL)

I'm sure you know all about them, but here are the relevant settings:

    msgmni: The number of IPC message queue resources allowed (by default, 16).
    msgmnb: The size of each message (by default, 8,192 bytes).
    msgmax: The maximum total size of the messages in a queue (by default, 16,384 byte...

Stolen from https://access.redhat.com/site/articles/15423 .