Added docs for email sensor (#950)

* added docs for email sensor

* renamed to imap email content

* added missing file

source/_components/sensor.imap_email_content.markdown

@@ -0,0 +1,46 @@
+---
+layout: page
+title: "Imap E-mail Content"
+description: "Instructions how to integrate imap email content sensor into Home Assistant."
+date: 2016-09-09 12:30
+sidebar: true
+comments: false
+sharing: true
+footer: true
+ha_category: Sensor
+---
+
+
+The `imap email content` sensor platform will read emails from an imap email server and report them as a state change within Home Assistant.
+This is useful if you have a device that only reports its state via email.
+
+To enable this sensor, add the following lines to your `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  - platform: imap_email_content
+    server: imap.gmail.com
+    port: 993
+    name: Emails
+    username: USERNAME
+    password: PASSWORD
+    senders:
+      - example@gmail.com
+    value_template: TEMPLATE
+```
+
+Configuration variables:
+
+- **server** (*Required*): The IP address or hostname of the IMAP server.
+- **port** (*Required*): The port where the server is accessible.
+- **name** (*Optional*): Name of the IMAP sensor.
+- **username** (*Required*): Username for the IMAP server.
+- **password** (*Required*): Password for the IMAP server.
+- **senders** (*Required*): A list of sender email addresses that are allowed to report state via email. Only emails recieved from these addresses will be processed.
+- **value_template** (*Optional*): If specified this template will be used to render the state of sensor. If a template is not supplied the raw message body will be used for the sensor value. The following attributes will be supplied to the template:
+
+   * **from**: The from address of the email
+   * **body**: The body of the email
+   * **subject**: The subject of the email
+   * **date**: The date and time the email was sent