Add cli interface

[dvc94ch]

As a well behaved unix library it should have a cli :)

[coveralls]

Coverage increased (+9.7%) to 53.91% when pulling dc50307 on dvc94ch:cli into 9f53e95 on multiformats:digest.

[dvc94ch]

Also adds murmur3 support for #34

[dvc94ch]

@dignifiedquire what do you think?

[dignifiedquire]

Lets please not start using non rust hashes if we don't have to. I have murmur3 matching the original implementation in rust here: https://github.com/dignifiedquire/murmur3 (fork of another crate)

[dignifiedquire]

actually there was no fix, I just improved the api, so you could just use the original version here: https://github.com/stusmall/murmur3

[vmx]

The API changed quite a bit with the release of 0.10.0 so this would need a rebase. If you still have interest in providing a CLI, please make this PR (or create a new one) with the CLI changes only and without adding the murmur hashing (that should be a separate PR).

[dvc94ch]

I'll reopen if I get around to it, I think it would be useful to have

[vmx]

I agree that it would be useful, thanks!