Add --quiet option to ipfs add

License: MIT
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Add sharness test for ipfs add --quiet

License: MIT
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Merge pull request #372 from chriscool/add_quiet_flag

Implement the -q or --quiet flag to add with minimal output