Update hack/make.sh with slightly clearer output and a more precise "are we in the Docker container?" check

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Fix 2720 -- Expanded documentation for docker run.
Docker-DCO-1.1-Signed-off-by: Andy Rothfusz <github@developersupport.net> (github: metalivedev)
Address feedback from @jamtur01.
Docker-DCO-1.1-Signed-off-by: Andy Rothfusz <github@developersupport.net> (github: metalivedev)
Make get.docker.io install directions slightly better by telling user exactly how to add themselves to the "docker" group

As a bonus, if the user has run this script the way we recommend (ie, without "sudo" or "su", run as their user), we can actually give them the exact command they'll need with their correct username substituted appropriately.

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
add tests

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
fix convertion issues

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
 Fix fun Travis DCO check YAML parsing issues (especially with commit messages that start with any kind of whitespace, like this one intentionally does)

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
refactor all *FromJob functions

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Merge pull request #3833 from vieux/fix_env_conversion_issues

Fix env conversion issues in env
remove TestAllocateTCPPortLocalhost faillure in tests

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Merge pull request #3854 from vieux/fix_tests

remove TestAllocateTCPPortLocalhost faillure in tests
fix TestExitCode

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
- Fixed the last cli.call's parameter from CmdSearch

Docker-DCO-1.1-Signed-off-by: Roberto Hashioka <roberto.hashioka@docker.com> (github: rogaha)
Merge pull request #3859 from rogaha/add_missing_attributes

- Fixed the last cli.call's parameter from CmdSearch
add make test-integration

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Merge pull request #3858 from vieux/fix_testexitcode

fix TestExitCode
Merge pull request #3758 from metalivedev/2720-running

Fixes 2720
Merge pull request #3860 from vieux/integration_makefile

Add "make test-integration"
vagrant: added PRIVATE_NETWORK env var

Docker-DCO-1.1-Signed-off-by: Rafal Jeczalik <rjeczalik@gmail.com> (github: rjeczalik)
changed default value of getenvint to 0. fix tests

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)