Support files with randomised block option

[axiom]

I have a need to bunzip files created with the deprecated randomised option. The source code has a comment saying that we can add support for this if anybody complains. This is me "complaining" 🙇.

seek-bzip/lib/index.js

Lines 141 to 145 in b77fe92

	/* We can add support for blockRandomised if anybody complains. There was
	some code for this in busybox 1.0.0-pre3, but nobody ever noticed that
	it didn't actually work. */
	if (reader.read(1))
	_throw(Err.OBSOLETE_INPUT);

This comment does not seem to originate with this project, so I'm not sure if the offer still stands. Otherwise I assume a pull request supporting these types of files would be welcome?

(Every available bzip2 package on NPM appear to have this same limitation…)