add pip packagename for freebsd os

[noelmcloughlin]

# [[ -d /usr/ports/devel/py-pip ]] && echo "package name is 'devel/py-pip' on FreeBSD ports"
package name is 'devel/py-pip' on FreeBSD ports

# pip --version
pip 9.0.3 from /usr/local/lib/python2.7/site-packages (python 2.7)

[noelmcloughlin]

Thanks @aboe76

BTW, this commit did not cause Travis CI failure on Debian. #151 or later must fix.

      ID: docker package
           Function: pkg.installed
               Name: lxc-docker
             Result: False
            Comment: Problem encountered installing package(s). Additional info follows:
              
              errors:
                  - Running scope as unit run-ra175ea52911141cda8ef18a5f1224071.scope.
                    E: Version '1.13.1*' for 'lxc-docker' was not found
            Started: 12:20:33.173803
           Duration: 36251.393 ms
            Changes: