Adds docs for Pollen.com sensor platform (#4524)

* Adds docs for Pollen.com sensor platform

* Updating version number

source/_components/sensor.pollen.markdown

@@ -0,0 +1,81 @@
+---
+layout: page
+title: "Pollen.com"
+description: "Instructions on how to use Pollen.com data within Home Assistant"
+date: 2018-01-10 19:20:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: pollen.jpg
+ha_category: Health
+ha_release: 0.63
+ha_iot_class: "Cloud Polling"
+---
+
+The `pollen` sensor platform collects and displays allergy and disease
+information (based on a U.S. ZIP code) from [Pollen.com](https://www.pollen.com/). Data measured includes:
+
+* Indicies for allergies and cold/flu measurements
+* Trends
+* Current outlook
+* more!
+
+## {% linkable_title Configuring the Platform %}
+
+To integrate `pollen` into Home Assistant, add the following section to your
+`configuration.yaml` file (adjusting the `monitored_conditions` list to your
+liking):
+
+```yaml
+sensor:
+  platform: pollen
+  zip_code: ZIP_CODE
+  monitored_conditions:
+    - allergy_average_forecasted
+    - allergy_average_historical
+    - allergy_index_today
+    - allergy_index_tomorrow
+    - allergy_index_yesterday
+    - disease_average_forecasted
+```
+
+{% configuration %}
+  zip_code:
+    description: the U.S. ZIP code to gather data for
+    required: true
+    type: int
+  monitored_conditions:
+    description: the metric types to monitor; valid values are specified below
+    required: true
+    type: list
+{% endconfiguration %}
+
+## {% linkable_title Available Metrics %}
+
+The following metrics can be monitored:
+
+* Allergy Index: Forecasted Average (`allergy_average_forecasted`): the average
+forecasted allergy index over the next 5 days
+* Allergy Index: Historical Average (`allergy_average_historical`): the average
+historical allergy index over the past 30 days
+* Allergy Index: Today (`allergy_index_today`): the allergy index for today
+* Allergy Index: Tomorrow (`allergy_index_tomorrow`): the allergy index for
+tomorrow
+* Allergy Index: Yesterday (`allergy_index_yesterday`): the allergy index for
+yesterday
+* Cold & Flu: Forecasted Average (`disease_average_forecasted`): the average
+forecasted cold/flu index over the next 5 days
+
+## {% linkable_title Understanding the Indices %}
+
+Any index-related sensor will have a value between 0.0 and 12.0. The values
+map to the following human-friendly ratings:
+
+Range      | Rating
+---------  | -----------
+0.0 - 2.4  | Low
+2.5 - 4.8  | Low/Medium
+4.9 - 7.2  | Medium
+7.3 - 9.6  | Medium/High
+9.7 - 12.0 | High