Update build and test dependencies. Test with Octane and Classic.

[krisselden]

• update ember cli
• migrate to new testing helpers
• migrate from ember-fastboot-addon-tests to ember-cli-fastboot-testing
• test in LTS and with octane and classic defaults

[krisselden]

I also need to figure out the fastboot tests

[krisselden]

@lukemelia I fixed the missing readme and I migrated the fastboot tests to ember-cli-fastboot-testing.

I also reduced some test dependence on jquery but I didn't quite remove it, since a lot of tests use the 'contains' selector.

[lukemelia]

🎉