Add performance tests

[twolfson]

During the development of gifsockets, performance was a major priority. We should embrace performance driven development as a core principle for this repository.

Things to perf:

• Verify using ByteCapacitor over pushing for every byte is more efficient
  • Test via both .read() and .on('data')
• Switch to ndarray over typed arrays for NeuQuant

[twolfson]

• Reuse of indexedPixels instead of reallocating them for every analyzePixels

[twolfson]

• Performance of removing alpha channel vs iterating of rgba array (this.pixels)
  • https://github.com/twolfson/gif-encoder/blob/0.3.0/README.md#setimagepixelspixels-options

[twolfson]

In 0.4.1, we discovered that frame based buffers are required since byte by byte buffers will fall over. This takes care of the first bullet point.