[WIP] Documentation updates targeted at new users evaluating kip

[unbracketed]

First pass at filling out user documentation:

• Add a section with common use cases
• Edit install instructions
• More accurate SYNOPSIS (IMO)

[unbracketed]

I see that in a few places the raw syntax didn't translate to what I intended after markdown. Will fix soon

[grahamking]

This looks great! Let me know when you think it's ready and I'll be happy to merge. Thanks!