Add continous integration through travis-ci.org
Get rid of custom ordered dict

Fix #8
Open the output file in binary mode

p_last.stdout is open in binary mode. Therefore, in Python 3,
p_last.stdout.read() returns bytes(). path should be open in binary for
cpyfileobj() to be able to write the buffer into the destination in
Python 3.
Close every file descriptor before raising

If we piped:
  ls | grep something | anothercommand

anothercommand's stdout wasn't getting closed.