Edit WUnderground markdown (#880)

Correcting some typos, capitalizing some letters, and improving some sentence structures

source/_components/sensor.wunderground.markdown

@@ -14,10 +14,10 @@ ha_iot_class: "Cloud Polling"
 ---
 
 
-The `wunderground` platform uses [Weather Underground](http://www.wunderground.com) as an source for current weather information. 
+The `wunderground` platform uses [Weather Underground](http://www.wunderground.com) as a source for current weather information. 
 
 <p class='note warning'>
-Obtain WUnderground API [here](https://www.wunderground.com/weather/api). Free account allows 500 requests per day or 10 per minute.
+Obtain a WUnderground API key [here](https://www.wunderground.com/weather/api). A free account allows 500 requests per day or 10 per minute.
 </p>
 
 To add Wunderground to your installation, add the following to your `configuration.yaml` file:
@@ -61,20 +61,20 @@ sensor:
 
 Configuration variables:
 - **api_key** (Required): See above
-- **pws_id** (Optional): You can enter your PWS id. Current list of Wunderground PWS stations is available [here](https://www.wunderground.com/weatherstation/ListStations.asp). If you do not enter the PWS ID, the current location information (latitude and longitude) from your `configuration.yaml` will be used to display weather conditions. 
+- **pws_id** (Optional): You can enter a Personal Weather Station id. The current list of Wunderground PWS stations is available [here](https://www.wunderground.com/weatherstation/ListStations.asp). If you do not enter a PWS ID, the current location information (latitude and longitude) from your `configuration.yaml` will be used to display weather conditions. 
 - **monitored_conditions** array (*Required*): Conditions to display in the frontend. The following conditions can be monitored.
   - **weather**: A human-readable text summary with picture from Wunderground.
   - **temp_f**: Current temperature in Fahrenheit
   - **temp_c**: Current temperature in Celsius
   - **station_id**: Your personal weather station (PWS) ID
-  - **feelslike_c**: Feels like (or apparent) temperature in celsius
+  - **feelslike_c**: Feels like (or apparent) temperature in Celsius
   - **feelslike_f**: Feels like (or apparent) temperature in Fahrenheit
-  - **feelslike_string**: Text summary of how the current teperature feels like
+  - **feelslike_string**: Text summary of how the current temperature feels like
   - **heat_index_c**: Heat index (combined effects of the temperature and humidity of the air) in Celsius
   - **heat_index_f**: Heat index (combined effects of the temperature and humidity of the air) in Fahrenheit
   - **heat_index_string**: Text summary of current heat index
-  - **dewpoint_c**: Temperature in celsius below which water droplets begin to condense and dew can form
-  - **dewpoint_f**: Temperature in fahrenheit below which water droplets begin to condense and dew can form
+  - **dewpoint_c**: Temperature in Celsius below which water droplets begin to condense and dew can form
+  - **dewpoint_f**: Temperature in Fahrenheit below which water droplets begin to condense and dew can form
   - **dewpoint_string**: Text summary of dew point
   - **wind_kph**: Current wind speed in kph
   - **wind_mph**: Current wind speed in mph
@@ -83,7 +83,7 @@ Configuration variables:
   - **pressure_mb**: Atmospheric air pressure in millibars
   - **wind_dir**: Wind direction
   - **wind_string**: Text summary of current wind conditions
-  - **relative_humidity**: Reltive humidity
+  - **relative_humidity**: Relative humidity
   - **visibility_mi**: Average visibility in miles
   - **visibility_km**: Average visibility in km
   - **precip_today_in**: Total precipitation in inches