When a default route gateway is specified, also route all multicast via the bridge interface
Support routing any number of networks via the container interface
o Document the new --route ... option
o Parse arguments a with more flexibilty, and full backward compatibilty
o Clean up conditionals to use if ...; then instead of short-circuit
o Quote variable tests
o Log a play-by-play if -v|--verbose option given
Report if unable to create files/links required, and suggest sudo
Corrected removal of default route before ip up; ignores failure
Copy "use libcontainer" pull request
o Shamelessly copy https://github.com/jpetazzo/pipework/pull/41, and modify
  it to more simply fall-back to docker if cgroups lookup doesn't work.
o Ensure we properly test for failures when seeking data from cgroups
  or docker, to avoid silent failure due to the "set -e"
o Consolidate all indentation to use spaces instead of inconsistent tabs
Consolidate all error, warning and debug logging, and emit to stderr