Fix failing tests due to modifications to imperatives

[sambhav]

With the recent addition of "initiate" to the list of imperatives,
both "initialize" and "initiate" stem to the same verb - "initi"
which causes an error since we use Initialize in our docs and due
to the way the imperative suggestion logic is implemented.

Since initiate occurs later in the file - when constructing a
dictionary - it trumps initialize and replaces it.

This patch fixes it by changing the dictionary to a list of verbs
instead of a single stem-verb map.

Thanks for submitting a PR!

Please make sure to check for the following items:

• Add unit tests and integration tests where applicable.
  If you've added an error code or changed an error code behavior,
  you should probably add or change a test case file under tests/test_cases/ and add
  it to the list under tests/test_definitions.py.
  If you've added or changed a command line option,
  you should probably add or change a test in tests/test_integration.py.
• Add a line to the release notes (docs/release_notes.rst) under "Current Development Version".
  Make sure to include the PR number after you open and get one.

Please don't get discouraged as it may take a while to get a review.

[sambhav]

@Nurdok with the latest push to the master - the tests broke. Can you take a look at this PR which fixes the test?

Because of the master all the other PRs are failing as well.

[sambhav]

NVM, didn't see there was an open PR #382 which does this in a much better way. Closing this.