Update README.md

Add RedBearLab nRF51822 link

Author: sandeepmistry

README.md

@@ -8,6 +8,7 @@ Program [Nordic Semiconductor](https://www.nordicsemi.com) nR5 based boards with
    * For boards prior to ```2016.9``` (see sticker), the lastest JLink bootloader is required to upload sketches. To upgrade, press the boot/reset button while powering on the board and copy over the latest [bootloader](https://www.nordicsemi.com/eng/nordic/Products/nRF52-DK/nRF5x-OB-JLink-IF/52275).
  * [Bluz DK](http://bluz.io)
  * [RedBearLab BLE Nano](http://redbearlab.com/blenano/)
+ * [RedBearLab nRF51822](http://redbearlab.com/redbearlab-nrf51822/)
 
 ## Installing