Add ubus platform and update blog post for 0.7.6

source/_components/device_tracker.ubus.markdown

@@ -0,0 +1,58 @@
+---
+layout: component
+title: "OpenWRT (ubus)"
+description: "Instructions how to integrate OpenWRT routers into Home Assistant."
+date: 2015-03-23 19:59
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: openwrt.png
+ha_category: Presence Detection
+---
+
+_This is one of the two ways we support OpenWRT. If you encounter problems, try [luci](/components/device_tracker.luci.html)._
+
+This is a presence detection scanner for OpenWRT using [ubus](http://wiki.openwrt.org/doc/techref/ubus).
+
+Before this scanner can be used you have to install the ubus RPC package on OpenWRT:
+
+```bash
+opkg install rpcd-mod-file
+```
+
+And create a read-only user to be used by setting up the ACL file `/usr/share/rpcd/acl.d/user.json`.
+
+```json
+{
+  "user": {
+    "description": "Read only user access role",
+    "read": {
+      "ubus": {
+        "*": [ "*" ]
+      },
+      "uci": [ "*" ]
+    },
+    "write": {}
+  }
+}
+```
+
+After this is done, configure Home Assistant as follows:
+
+```yaml
+# Example configuration.yaml entry
+device_tracker:
+  platform: ubus
+  host: ROUTER_IP_ADDRESS
+  username: YOUR_ADMIN_USERNAME
+  password: YOUR_ADMIN_PASSWORD
+```
+
+Configuration variables:
+
+- **host** (*Required*): The IP address of your router, e.g. 192.168.1.1.
+- **username** (*Required*): The username of an user with administrative privileges, usually *admin*.
+- **password** (*Required*): The password for your given admin account.
+
+See the [device tracker component page](/components/device_tracker.html) for instructions how to configure the people to be tracked.