Added framework in which integration tests can be run.
Simplified the integration test framework by removing the fixture manager.
Added integration tests for the case of the proxy being up. Still need to auto-spawn proxy.
Proxy is now auto-spawned. Moved integration tests to a top-level folder.
Merge branch 'master' of github.com:teamfruit/defend_against_fruit into integration_tests

* 'master' of github.com:teamfruit/defend_against_fruit:
  Added command-line option (--skip-int-tests) to skip running integration tests. Note that this option will not flow down to each submodule in a multi-module build.
  Updated fruit_dist so that it optionally takes an integration test function to be run after the package is built.
Moved integration tests to be part of the standard_sdist_run (required an update of fruit-dist dependencies to 1.2.79).
Refactored integration tests.
Made integration tests more robust.
Added 404 test for non-existent file.
Refactored get-and-validate package tests.
Added "python/" Artifactory tests for the cached cases.
Added proxy tests.