Document bash completion in a usable way

[rholder]

Here is how we activate bash completion for csv2es after pip installing it:

eval "$(_CSV2ES_COMPLETE=source csv2es)"

This seems to work fine but presumably we'll install this in a virtualenv and keep it around for a while or some such so what's the best way to get it working when we install?

An alternative method is to create and drop this file somewhere for sourcing (but where....?):

_CSV2ES_COMPLETE=source csv2es > csv2es-complete.sh

There are more details here.