Add a cuke for mobile stream page post timestamps

features/mobile/stream.feature

+@javascript @mobile
+Feature: Viewing the main stream mobile page
+
+  Background:
+    Given following users exist:
+      | username   |
+      | alice      |
+      | bob        |
+    And a user with username "bob" is connected with "alice"
+    And "alice@alice.alice" has a public post with text "Hello! I am #newhere"
+
+  Scenario: Show post with correct timestamp
+    When I sign in as "bob@bob.bob" on the mobile website
+    And I go to the stream page
+    Then I should see "Hello! I am #newhere" within ".ltr"
+    And I should see "less than a minute ago" within "#main_stream"