Refactor to use compositor

:warning: not ready for merge

After watching the 2013 WWDC video on AVFoundation I got this idea to use instructions/compositions/etc. to cleanup this project and handle the logic better, while making it easier to incorporate tracks like audio.

The idea I outlined looks like this:

- Create new comp
- Set timing to `1 / (2x - 1)` fps (where x is input fps)
- Add input video track 2 times
  - Second addition is added at +1 frame offset
- Generate array of instructions (might look like the following)

```text
Input frame           1             2             3             4
Output frame          1      2      3      4      5      6      7

Tracks:

                    -------------------------------------------
                    |      |      |      |      |      |      |
Prior               |  X   |      |      |      |      |      |
                    |      |      |      |      |      |      |
                    --------------------------------------------------
                           |      |      |      |      |      |      |
Inbetween                  |  X   |      |  X   |      |  X   |      |
                           |      |      |      |      |      |      |
                           -------------------------------------------
                           |      |      |      |      |      |      |
Next                       |      |  X   |      |  X   |      |  X   |
                           |      |      |      |      |      |      |
                           -------------------------------------------
```

**Prior** is source track, **Next** is source track at +1 frame offset, **Inbetween** is result of interpolation instruction. The **X** indicates where the frame is being taken from for the output composition.