Use zlib.createUnzip()

[piranna]

gunzip-maybe/index.js

Lines 19 to 28 in 6903d9c

	switch (isCompressed(data)) {
	case 1:
	swap(null, pumpify(zlib.createGunzip(), gunzip(maxRecursion - 1)))
	break
	case 2:
	swap(null, pumpify(zlib.createInflate(), gunzip(maxRecursion - 1)))
	break
	default:
	swap(null, through())
	}

It looks like createUnzip() already does detection between Gunzip and Inflate, so there's no need to do it ourselves, reducing code size and number of dependencies.

[piranna]

Also, since this project is not just Gunzip-only anymore, maybe should it be renamed to unzip-maybe? :-)