add docs for etherscan and blockchain sensors (#2734)

source/_components/sensor.blockchain.markdown

@@ -0,0 +1,32 @@
+---
+layout: page
+title: "Blockchain.info"
+description: "Instructions how to integrate Blockchain.info data within Home Assistant."
+date: 2017-06-01 16:20
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: blockchain.png
+ha_category: Finance
+ha_release: 0.46
+ha_iot_class: "Cloud Polling"
+---
+
+
+The `Blockchain` sensor platform displays Bitcoin wallet balances from [blockchain.info](https://blockchain.info).
+
+To add the Blockchain sensor to your installation, specify a list of bitcoin addresses to watch in the `configuration.yaml` file.  The sensor state will be the sum of the balances of all addresses listed.
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  - platform: blockchain
+    addresses:
+      - '1BMsHFczb2vY1BMDvFGWgGU8mkWVm5fupp'
+      - '183J5pXWqYYsxZ7inTVw9tEpejDXyMFroe'
+```
+
+Configuration variables:
+
+- **addresses** (*Required*): List of bitcoin wallet addresses to watch 

source/_components/sensor.etherscan.markdown

@@ -0,0 +1,30 @@
+---
+layout: page
+title: "Etherscan"
+description: "Instructions how to integrate Etherscan.io data within Home Assistant."
+date: 2017-06-01 16:20
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: etherscan.png
+ha_category: Finance
+ha_release: 0.46
+ha_iot_class: "Cloud Polling"
+---
+
+
+The `Etherscan` sensor platform displays Ethereum wallet balances from [Etherscan.io](https://etherscan.io).
+
+To add the Etherscan sensor to your installation, specify an ethereum address to watch in the `configuration.yaml` file:
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  platform: etherscan
+  address: '0xfB6916095ca1df60bB79Ce92cE3Ea74c37c5d359'
+```
+
+Configuration variables:
+
+- **address** (*Required*): Ethereum wallet address to watch