Add WiFi fast connect (#121)

Author: OttoWinter

esphomeyaml/components/wifi.rst

@@ -65,6 +65,8 @@ Configuration variables:
   seems to have issues with WiFi where a full reboot is required to get the interface back working. Defaults to ``5min``.
 - **power_save_mode** (*Optional*, string): The power save mode for the WiFi interface. Defaults to no power saving.
   See :ref:`wifi-power_save_mode`
+- **fast_connect** (*Optional*, boolean): If enabled, directly connects to WiFi network without doing a full scan
+  first. This is required for hidden networks and can significantly improve connection times. Defaults to ``off``.
 - **id** (*Optional*, :ref:`config-id`): Manually specify the ID used for code generation.
 
 Access Point Mode

esphomeyaml/guides/faq.rst

@@ -234,6 +234,7 @@ not have a real solution.
 Some steps that can help with the issue:
 
 -  Set the ``power_save_mode`` to ``light`` in the ``wifi:`` config. See :ref:`wifi-power_save_mode`.
+-  If you're using a hidden WiFi network, make sure to enable ``fast_connect`` mode in the WiFi configuration.
 -  Use the most recent version of th arduino framework. The platformio arduino package
    always takes some time to update and the most recent version often includes some awesome
    patches. See :ref:`esphomeyaml-arduino_version`.