This change keeps the lumi prefix on our CLI tools.
As @lukehoban pointed out in person, as soon as we do pulumi/coconut#98,
most people (other than compiler authors themselves) won't actually be
typing the commands. And, furthermore, the commands aren't all that bad.
Eventually I assume we'll want something like `lumi-js`, or
`lumi-js-compiler`, so that binaries are discovered dynamically in a way
that is extensible for future languages. We can tackle this during #98.
This restructures the examples directory a bit, into three buckets:
* basic/: simplistic examples, like hello world and whatnot.
* conversions/: actual conversions from existing samples (with the source cited).
* scenarios/: more complex examples that demonstrate various features of the system.
