This allows the chunking algorithm, and options to be specified when using the adding files.
Specifying chunker and options are identical to go-ipfs and support the following formats:
default, size-{size}, rabin, rabin-{avg}, rabin-{min}-{avg}-{max}
This is required to achieve parity with go-ipfs.

Fixes #1283

License: MIT
Signed-off-by: Dan Ordille <dordille@gmail.com>