PMSx003 does not work

[hajdbo]

Operating environment/Installation (Hass.io/Docker/pip/etc.):

Hass.io

ESP (ESP32/ESP8266/Board/Sonoff):

ESP8266 with PMS7003

Affected component:

PMSx003

Description of problem:
PMSx003 module does not work, as the payload_size computing is wrong:

// start (16bit) + length (16bit) + DATA (16bit) + checksum (16bit)
  uint8_t total_size = 4 + payload_length * 2 + 2;

payload_length is actually number of bytes, including checksum.

Problem-relevant YAML-configuration entries:

esphomeyaml:
  name: mqttbme280pms7003
  platform: ESP8266
  board: nodemcuv2
  on_boot:
    then:
        - output.turn_on: gpio_d2

wifi:
    ssid: 'XXXXX'
    password: 'XXXXXX'

logger:

api:
  port: 6053

uart:
  rx_pin: D1
  baud_rate: 9600

# D2 is set pin on particle sensor
output:
  - platform: gpio
    pin: D2
    id: gpio_d2

sensor:
  - platform: pmsx003
    type: PMSX003
    pm_1_0:
      name: "Particulate Matter <1.0µm Concentration"
    pm_2_5:
      name: "Particulate Matter <2.5µm Concentration"
    pm_10_0:
      name: "Particulate Matter <10.0µm Concentration"

Traceback (if applicable):

Additional information:
I'll submit a PR to compute the correct payload length