Don't skip consecutive newlines

I guess I forgot that blank newlines are important for the RFC822 file
format as they sometimes serve as seperators, so I can't skip them.
Add a (rudimentary) show command

The general idea here is that I want to easily test my message parsing
code without needing to contact Google every single time I want to run
a test.  I figured that, as I'd need to write scan anyway, that I
might as well start now!

This current version of the code doesn't do any fancy message parsing
stuff (like lookup names in my address book), but it does at least let
me pull out (some) of the headers from a message!