Add adblock dependency to README, version.py, remove from setup.py

README.asciidoc

@@ -133,6 +133,7 @@ The following software and libraries are required to run qutebrowser:
 
 The following libraries are optional:
 
+* https://pypi.org/project/adblock/[adblock] (for Ad-blocking using ABP syntax)
 * http://cthedot.de/cssutils/[cssutils] (for an improved `:download --mhtml`
   with QtWebKit).
 * On Windows, https://pypi.python.org/pypi/colorama/[colorama] for colored log

qutebrowser/utils/version.py

@@ -224,6 +224,7 @@ def _module_versions() -> typing.Sequence[str]:
         ('jinja2', ['__version__']),
         ('pygments', ['__version__']),
         ('yaml', ['__version__']),
+        ('adblock', ['__version__']),
         ('cssutils', ['__version__']),
         ('attr', ['__version__']),
         ('PyQt5.QtWebEngineWidgets', []),

setup.py

@@ -71,7 +71,7 @@ try:
         entry_points={'gui_scripts':
                       ['qutebrowser = qutebrowser.qutebrowser:main']},
         zip_safe=True,
-        install_requires=['pypeg2', 'jinja2', 'pygments', 'PyYAML', 'attrs', 'adblock'],
+        install_requires=['pypeg2', 'jinja2', 'pygments', 'PyYAML', 'attrs'],
         python_requires='>=3.5',
         name='qutebrowser',
         version=_get_constant('version'),