Add a plug logo

Resolves #40

Author: Tyler Goodlet

docs/_static/img/plug.png

@@ -33,7 +33,19 @@
 language = None
 
 pygments_style = 'sphinx'
+html_logo = '_static/img/plug.png'
 html_theme = 'alabaster'
+html_theme_options = {
+    # 'logo': 'img/plug.png',
+    # 'logo_name': 'true',
+    'description': 'The `pytest` plugin system',
+    'github_user': 'pytest-dev',
+    'github_repo': 'pluggy',
+    'github_button': 'true',
+    'github_banner': 'true',
+    'page_width': '1080px',
+    'fixed_sidebar': 'false',
+}
 html_static_path = ['_static']
 
 # One entry per manual page. List of tuples