Add gemfiles for dj 3.x and 4.x for travis
Allow delayed job 3 tests to fail

* Until we can get them passing...
Explicitly require lib from test file
Simplify db setup for tests

* Rather than having a skeleton Rails app, this just creates a table to
  back the Delayed::Job model. Just enough to keep tests green :+1:
Remove unneeded "skeleton" rails app

* No longer needed! :boom:
Remove allowable failures

* DJ 3.x CI fixed :+1:
Merge pull request #5 from iamvery/dj3-travis

Delayed job 3.x CI