Docker support and more AVX

In addition to the baseline x86_64 SIMD support, we've added a couple extra builds, one with AVX and another with even more AVX thrown in. Like AVX_2_.

If you have a Skylake, Broadwell, Haswell, Ivy Bridge, or Sandy Bridge (2011+) CPU, try the -sandybridge- build for Linux. It requires AVX support, which the aforementioned families have (if you avoid Celeron-branded stuff).
If you have Haswell, Broadwell, or Skylake, try the -haswell- build, which requires AVX2 & friends.

Excluding perhaps t2.micro, all AWS, Azure, and Digital Ocean virtual machines should be Sandy Bridge or higher (most are actually Haswell or higher).

We're using the sandybridge build for our Docker Cloud demo. Most Digital Ocean servers support Haswell, but not all. #92 (comment)