Add a simple end2end test for :adblock-update

tests/end2end/data/adblock/simple

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+example.org

tests/end2end/features/adblock.feature

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+Feature: Ad blocking
+
+    Scenario: Simple adblock update
+        When I set up "simple" as block lists
+        And I run :adblock-update
+        Then the message "adblock: Read 1 hosts from 1 sources." should be shown

tests/end2end/features/test_adblock_bdd.py

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+# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:
+
+# Copyright 2016 Florian Bruhin (The Compiler) <mail@qutebrowser.org>
+#
+# This file is part of qutebrowser.
+#
+# qutebrowser is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# qutebrowser is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.
+
+import pytest_bdd as bdd
+
+bdd.scenarios('adblock.feature')
+
+
+@bdd.when(bdd.parsers.parse('I set up "{lists}" as block lists'))
+def set_up_blocking(quteproc, lists, httpbin):
+    url = 'http://localhost:{}/data/adblock/'.format(httpbin.port)
+    urls = [url + item.strip() for item in lists.split(',')]
+    quteproc.set_setting('content', 'host-block-lists', ','.join(urls))