Add dependencies to com.android.support.test.rules and runner

[whym]

Add dependencies to com.android.support.test.rules and runner

Fixes #1574 (SettingsActivityTest fails due to undeclared dependencies).

Description

• Adds dependencies needed for ActivityTestRule used in SettingsActivityTest.
  • Not sure why it was okay previously without them, but it is apparently required now as described in SettingsActivityTest fails due to undeclared dependencies #1574.
  • The gradle lines were taken from https://developer.android.com/training/testing/packages#android-test-dependencies .

Tests performed

• Local unit tests - no error
• Travis-CI tests (from my account) - pass

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@30e5312). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff            @@
##             master   #1575   +/-   ##
========================================
  Coverage          ?   3.91%           
========================================
  Files             ?     146           
  Lines             ?    7450           
  Branches          ?     714           
========================================
  Hits              ?     292           
  Misses            ?    7141           
  Partials          ?      17

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