[bug 1032967] Handle unsupported language pairs

Previously we looked at the Gengo service languages list to see if the
src language was supported and went with that. However, that wasn't
correct and created problems. We really need to see if the (src, dst)
pair is supported.

This fixes that.
[bug 1026503] First pass at vagrantification

* adds vagrant stuff and provision scripts
* first pass at overhauling docs to use Vagrant rather than explicitly
  walk through how to set up a Fjord development environment
Continued working on docs; ditched hacking howto
Assume VB mismatch and codify the fix in the docs

Ian pointed out that most people will have a mismatch, so we should be
pro-active about that and address it in the docs before provisioning.
This adds the necessary bits to the docs plus it removes the note from
the provisioning script.
[Bug 1030905] fjord feedback api tests for dates

Test the get api when filtering by date.
Add the following tests:
* test_date_start
* test_date_end
* test_date_delta_with_date_end
* test_date_delta_with_date_start
* test_date_delta_with_date_end_and_date_start
* test_date_delta_with_no_constraints
And the following helper method:
* create_test_data
pep8 compliance for fjord feedback api tests
 Revise according to review comments

    * Comments should use hashes not triple quoted strings
    * The data should already be sorted, and does not need to be sorted again
    * As a result, all of the expected indexes had to be switched
    * Add beforeyesterday data value to test_date_delta_with_no_constraints
    * Change docstring for test_date_delta_with_no_constraints
https://github.com/mozilla/fjord/pull/319
Refactoring: remove redundant logic

Split repetetive test logic into a helper method.
Add a method to test date_start, and date_end but no date_delta
_test helper method calls create_test_data

Reduces code duplication.
Make new code more pythonic

Easier on the eyes and passes flake8. Remove trailing parens and long
namespaces paths.
Improve readability by reordering test data
Refactor tests according to Will's comments

* Rewrite several docstrings and method names
* Remove extaneous comments
* Remove sorting - data should be sorted by default
* As a result, refactor the expected order of most test data
Update test data and docstrings

* Change docstring for test_date_delta_with_date_start
* Change docstring for test_date_delta_with_date_end_and_date_start
* Change test data in test_date_delta_with_date_end so it is in the
	middle of the dataset.
Merge branch '1030905-more-api-tests' of github.com:iankronquist/fjord into 1030905-more-api-tests