Update readme

[andkay]

Overhauled the Readme.

• removed all redundant accounting of handlers
• Moved usage stuff toward the top
• Lumped config option reference in with advanced config
• other changes to enhance clarity.

I think its a definite improvement -- but maybe one more pass needed.

[andkay]

@fredshone good catches all. turns out its pretty easy to miss things restructuring large .md

made the above changes plus a few add'l.