Escape control and nonprintable characters in docker ps

The docker ps command displays the user-entered command running in a container.
If that command contained \n, \t, or other control characters, they were
interpreted literally, and newlines and tabs would be printed in the output.
Escape the command string to make things more readable.

Docker-DCO-1.1-Signed-off-by: Matt Heon <mheon@redhat.com> (github: mheon)
Skip lxc_template_unit_test.go on non-Linux platforms

It doesn't work without lxc-start.

Docker-DCO-1.1-Signed-off-by: Kato Kazuyoshi <kato.kazuyoshi@gmail.com> (github: kzys)
Update the Travis GitHub username regex to match the GitHub username requirements

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #6573 from mheon/ps_cleanup

Escape control and nonprintable characters in docker ps
Merge pull request #6878 from tianon/update-travis-github-username-regex

Update the Travis GitHub username regex to match the GitHub username requirements
Merge pull request #6756 from kzys/lxc-linux

Skip lxc_template_unit_test.go on non-Linux platforms