fix: io.js 3.0 - Node.js 5.3 typed array support

[ChALkeR]

1. Between io.js 3.0 and Node.js 5.3, typed arrays are supported, but Buffer(ab, offset, length) wasn't. So add a recheck for that case.
2. Between io.js 3.0 and Node.js 4.4, this also hit Buffers, as they are not passing fast-path instanceof check there
   Which was a regression in [Fix] return valid values on multi-byte-wide TypedArray input #23
3. Between Node.js 5.0 and 6.3.0, Buffer(new Uint8Array(0).buffer) fails on empty buffers, add a hack for that
4. Also refactor code a bit

Refs: browserify/hash-base#19

[ljharb]

LGTM after some added tests