QA update feature descriptions for messages test

Cucumber Scenario and Feature description are just plain text.
Instead of using comments, it is far better to describe in each
test step what should happen in each test step.

I believe I have described these test steps correctly. Please
advise if they need to be tweaked.

(The test itself seems to be fine, but feel free to review that
also)

Finally, since messages.feature uses the "I have no new notifications"
step, I updated those assertions for modern RSpec syntax

Change-Id: Ie884a85c1fc3f7045773a271a8d76fad6b0b3826
Merge "QA update feature descriptions for messages test"