WIP Documented acceptance testing

[ghost]

🚨 Do not merge, work in progress 🚨

First steps towards setting up a standard practice for acceptance testing with EmberFire. This should include:

• new docs including example test code, and
• test helpers and blueprints that match existing ember acceptance testing patterns.

Progress:

• Define an acceptance test module for Qunit, add to emberfire blueprint.
• Add docs for standard approach including instructions for fixture data
• Add module definition and example test for Mocha users.
• Add access to the firebase ref in the acceptance test
• Add instructions for handling changes to data, e.g. updates, additions, deletions
• Manually test example code with a basic ember app.

Potentially out of scope:

• Add acceptance tests to the dummy app
• Consider implications of trying to stub multiple Firebase instances.
• Updating Emberfire's acceptance tests to use the new module.

Notable considerations:

• ember-cli is moving test helpers to individual test libraries.

N.B. merging into branch acceptance-testing

cc @tstirrat

[ghost]

Related to #349

[villander]

Awesome @binhums 💃

[jemware]

+1

[googlebot]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for the commit author(s). If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.

[googlebot]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for the commit author(s). If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.

[tstirrat]

Going to squash and merge this into another branch to clean it up (CLA errors are due to my own email being misconfigured on github)

[tonycoco]

Any plan to add this? Also needed would be auth mocks.

[tpetrone]

Any updates?