Add a simple testcase that shows we can import modules from other files.

[eholk]

This will also let us avoid a lot of boilerplate code in subsequent tests.

Issue #29

[lqd]

nice

it'd probably be good to have the "more correct paths" for the core traits (which the hello world examples doesn't have, but most of the others do) since those are the ones #[derive()] expects for instance. It probably won't matter mid to long term, if/when we can compile part of libcore/std though.

[brson]

Thanks @eholk !