Add support for piped input

Piped input when no additional arguments given or the first input is a
dash (-).
Fix pipe flushing

Reading input in a while loop for unbuffered reading and flush the
output as soon as the result has been written. This way you can do
something like
curl localhost | python hashid.py | grep +
and analyze hashes as soon as first command spits them out
Merge pull request #15 from maxg0/master

Add support for pipes