* Add support for multiple serial gateways.
* Fix serialization of python objects by adding dict representation of
classes.
* Add support for showing more than one child value type per entity.
The entity state is always only one value type. This is defined by
the platform value types. Value types that are not defined as the
platform value type are shown as state_attributes.
* Add more unit of measurement types.
* Clean up code.
* Add a general mysensors component. This sets up the serial comm
with the gateway through pymysensors. The component also
contains a decorator function for the callback function of
mysensors platforms. Mysensors platforms should create a
function that listens for the node update event fired by the
mysensors component. This function should call another
function, that uses the decorator, and returns a dict. The dict
should contain a list of which mysensors V_TYPE values the
platform handles, the platfrom class and the add_devices
function (from setup_platform).
* Change existing mysensors sensor platform to depend on the new
mysensors component.
* Add a mysensors switch platform. The switch platform takes
advantage of new functionality from the the fork of pymysensors
https://github.com/MartinHjelmare/pymysensors, that enables the
gateway to send commands to change node child values.
* Change const and is_metric to global constants, in the mysensors
component and import const depending on the mysensors version
used.
* Change variables devices and gateway to global variables.
* Add some debug logging at INFO log level.
