More idiomatic Go for shutting down goroutines

Apparently it's more idiomatic to use chan of interface{} and close them
rather than using a chan of bool and passing a message along it.

See
[here](https://groups.google.com/d/msg/golang-nuts/4bzn57zI_5I/-RJ9SvitS4wJ).
Whitespace, gofmt changes.
Add ability to specify addr and port to listen on

Add options to specify the address and port on which to listen.

Change the snippet into a text/template template so that we can fill in
the address and port at runtime.
Merge branch 'master' of https://github.com/hartzell/mdwiki-dev-server