Give "no messages" p an id for easier testing
[bug 933390] Add input-tests code

This adds the input-tests code from the willkg/input-tests repository
based on sha 5d2a05b.

Adding it to the fjord repository lets us tie versions of fjord to
changes/updates in the smoketests. This isn't designed to replace the
input-tests repository so much as it's designed to gives us
client-based smoketests which we're sorely lacking right now.
[bug 933390] Rework README to fit in fjord repository
[bug 933390] Fix input-stage url
[bug 933390] Remove test_ideas.py

We don't do ideas anymore--just happy and sad feedback.
[bug 933390] Update test_redirects
[bug 933390] Speed up the case where there are no messages

The test for no messages is pretty fast whereas the test for
len(feedback_pg.messages) kicks off a implicit wait which takes a while
to timeout if there are no messages.
[bug 933390] Re-add the platform property
[bug 933390] Update test_date_picker
[bug 933390] Minor cosmetic cleanup
Add results/ directory to .gitignore
Remove old ui test code

It didn't work because of other issues. Given we have smoke tests now,
seems like a good idea to just nix them.
Update docs regarding xvfb
Fix feedback sampledata to be more comprehensive
Update README.rst to cover generating data