ENH: add a from_configuration ctor for machine_cli.
TST: add some tests for file-based repositories.
TST: add tests for fs repositories at the command level.
MAINT: try using the new container-based env on travis-ci.
Merge pull request #447 from enthought/simplify_machine_cli

ENH: add a from_configuration ctor for machine_cli.
BUG: add linux3 for guess platform hack.
Merge pull request #451 from enthought/use_container_travis_ci

MAINT: try using the new container-based env on travis-ci.
ENH: update requests to 2.5.1.
Merge pull request #453 from enthought/update_requests_to_2.5.1

ENH: update requests to 2.5.1.