This commit adds support for the --api option, which allows users
to specify an API endpoint to run the cli command against. It enables
much easier control of remote daemons.

It also
- ensures the API server version matches the API client
- implements support for the $IPFS_PATH/api file

Still TODO:
- tests!
- multiaddr to support /dns/

License: MIT
Signed-off-by: Juan Batiz-Benet <juan@benet.ai>