Hackily fix compile errors in the tests.

[lye]

I'm not quite sure how to run the tests, but some things I probably did wrong:

• In the AudioTest, couldn't figure out the right way to pass an
  AudioClip to AudioAPI::play. The original test set up a background
  track; pretty sure AudioAPI::play doesn't quite do that.
• In the EntityTest, during TestState::init, a World reference is
  stolen from a unique_ptr. There's an API mismatch wherein createWorld returns a
  unique_ptr<World>, but StatsView::setWorld wants an unmanaged pointer
  (and doesn't take ownership of it). Stealing the pointer (via
  unique_ptr::release/unique_ptr::reset) is terrible, but I'm not sure
  how the ownership semantics should work.
• In the EntityTest, the mask passed to SpritePainter::add was 0; this
  causes the sprite to never be drawn (via SpritePainter::draw; the
  getMask() & mask check fails). I'm not entirely sure what the mask does,
  but setting it to 1 makes something (albeit incorrect) renders. I think
  the assets might be out-of-date? But the animation frames don't look
  like they have the right texture coordinates.

I believe this fixes #32

[amzeratul]

Hi there:

• Audio API has changed so you now play audio events instead of clips. Under assets_src/audio_event, you can declare a file e.g. myAudio.yaml, that contains something of the sort:

---
actions:
  - type: play
    clips: [ sfx/myAudio.ogg ]
    group: sfx
    pitch: [ 0.9, 1.1 ]
    volume: [ 0.9, 1.0 ]
    delay: 0.25
...

You can then play it by calling AudioAPI::play("myAudio").

• The World reference required that should be an observing pointer. It's a bit ugly and it should probably take a reference instead. Don't steal it from the unique pointer, but I guess rather take the address of the dereferenced (can't you .get() on a unique_ptr?)

• The sprite mask changed, it used to be a single number that the sprite had to match the camera; it's now a bitmask (therefore 0 will never get rendered)

[amzeratul]

Also, thank you very much for your contribution! :)

[lye]

Thanks for the feedback! I've updated the PR accordingly.

I'm not sure what was going on in my head with unique_ptr. Gonna blame that on sleepiness.