more ByteBufs, better allocator, less Unpooled

Should improve performance quite a bit.
build.gradle: stop tuning JIT on run
Message: memoize byte representation

Might not be useful, but won't be expensive either.
build.gradle: v3.1.0
Merge pull request #37 from airbnb/pierre/bytebufs_luv

v3.1.0: much better perf