Add HitBTC to exchanges.

_data/merchants.yml

@@ -4,6 +4,8 @@
       url: https://www.bittrex.com/Market/Index?MarketName=BTC-XMR
     - name: Bter
       url: https://bter.com/
+    - name: HitBTC
+      url: https://hitbtc.com/
     - name: Poloniex
       url: https://poloniex.com/exchange/btc_xmr
     - name: ShapeShift (instant)