Merge pull request #578 from shakyink/feature/gdax_api

Update - Added GDAX Trading Platform API

README.md

@@ -161,6 +161,7 @@ API | Description | Auth | HTTPS | Link |
 | CoinMarketCap | Cryptocurrencies Prices | No | Yes | [Go!](https://coinmarketcap.com/api/) |
 | CryptoCompare | Cryptocurrencies Comparison | No | Yes | [Go!](https://www.cryptocompare.com/api#) |
 | Cryptonator | Cryptocurrencies Exchange Rates | No | Yes | [Go!](https://www.cryptonator.com/api/) |
+| GDAX | Cryptocurrency Trading Platform | `apiKey` | Yes | [Go!](https://docs.gdax.com/#api) |
 | MercadoBitcoin | Brazilian Cryptocurrency Information | No | Yes | [Go!](https://www.mercadobitcoin.net/api-doc/) |
 
 ### Currency Exchange