scanner:  support a full shell for commands

Support a full shell for both the detection and scanning commands.  This
will allow much more complex configuration to be stored in the fzsl.conf
file rather than being separated out.

Resolves #13
bash:  make binding optional
bash:  allow user configuration of binding

Wrap the binding of fzsl inside of __fzsl_bind_default_matching and also
allow the user to specify the readline code to bind to.

Finally, switch to ctrl+p by default to prevent carpal tunnel.
bash:  add fzcd, fuzzy change directory
fzsl:  use setuptools for packaging

resolves #11