Add Docker.version
Add [attach], [Exec.create] and [Exec.start]

The multiplexed stream handling is yet to be written.
Close the file descriptor when raising an exception
Complete the module Stream
Transmit command + arguments as lists
Be more careful about the end of the streams
Report explanation in Server_error
Deal with status 500 when returning a stream
Improve documentation
Finalized the interface of Stream
Add some tests