Test to require that byte-order is specified
Test to require that byte-order is specified

By default `struct.unpack` assumes "native" byte order - ie platform
dependent. That's not very helpful when OpenPGP packets are a defined
byte order.

https://docs.python.org/2/library/struct.html#byte-order-size-and-alignment

I don't believe there's a useful case at the moment for using `unpack`
*without* specifying byte order (and this sloppiness allowed bug #5 to
slip through).

paulfurley/encryptit,paulfurley/encryptit