Add setting to change font. Change default to arial

Closes #33

youtube/__init__.py

@@ -66,3 +66,20 @@ def error_page(e):
             error_message += ' Exit node IP address: ' + exc_info()[1].ip
         return flask.render_template('error.html', error_message=error_message), 502
     return flask.render_template('error.html', traceback=traceback.format_exc()), 500
+
+font_choices = {
+    0: 'initial',
+    1: 'arial, "liberation sans", sans-serif',
+    2: '"liberation serif", "times new roman", calibri, carlito, serif',
+    3: 'verdana, sans-serif',
+    4: 'tahoma, sans-serif',
+}
+
+@yt_app.route('/shared.css')
+def get_css():
+    return flask.Response(
+        flask.render_template('shared.css',
+            font_family = font_choices[settings.font]
+        ),
+        mimetype='text/css',
+    )