Added urlview keybinding

1.  A shortcut of 'b' was used as the default binding for passing
comment body text to urlview (this is similar to the default of C-b in
the 'mutt' text email client)
2.  The `comment_urlview` SubmissionController function was added to
recieve the SUBMISSION_OPEN_IN_URLVIEWER keypress request.
3.  The `open_urlview` terminal function was added to handle the urlview
request.  It passes the comment body data to urlview via a Popen
process.
4.  A test case was added to ensure this new code path is executed
5.  Small formatting changes, mostly line length

tests/test_submission.py

@@ -253,4 +253,29 @@ def test_submission_edit(submission_page, terminal, refresh_token):
 
         submission_page.controller.trigger('e')
         assert open_editor.called
-        edit.assert_called_with('comment text')
+        edit.assert_called_with('comment text')
+
+
+def test_submission_urlview(submission_page, terminal, refresh_token):
+
+    # Log in
+    submission_page.config.refresh_token = refresh_token
+    submission_page.oauth.authorize()
+
+    # Positive Case
+    data = submission_page.content.get(submission_page.nav.absolute_index)
+    TEST_BODY = 'test comment body'
+    data['body'] = TEST_BODY
+    with mock.patch.object(terminal, 'open_urlview') as open_urlview, \
+            mock.patch('subprocess.Popen'):
+        submission_page.controller.trigger('b')
+        open_urlview.assert_called_with(TEST_BODY)
+
+    # Negative Case
+    data = submission_page.content.get(submission_page.nav.absolute_index)
+    TEST_NO_BODY = ''
+    data['body'] = TEST_NO_BODY
+    with mock.patch.object(terminal, 'open_urlview') as open_urlview, \
+            mock.patch('subprocess.Popen'):
+        submission_page.controller.trigger('b')
+        assert not open_urlview.called