Update CoinMarketCap Readme

CoinMarketCap does require an `apiKey`

README.md

@@ -184,7 +184,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Coinigy](https://coinigy.docs.apiary.io) | Interacting with Coinigy Accounts and Exchange Directly | `apiKey` | Yes | Unknown |
 | [CoinLayer](https://coinlayer.com) | Real-time Crypto Currency Exchange Rates | `apiKey` | Yes | Unknown |
 | [Coinlore](https://www.coinlore.com/cryptocurrency-data-api) | Cryptocurrencies prices, volume and more | No | Yes | Unknown |
-| [CoinMarketCap](https://coinmarketcap.com/api/) | Cryptocurrencies Prices | No | Yes | Unknown |
+| [CoinMarketCap](https://coinmarketcap.com/api/) | Cryptocurrencies Prices | `apiKey` | Yes | Unknown |
 | [Coinpaprika](https://api.coinpaprika.com) | Cryptocurrencies prices, volume and more | No | Yes | Yes |
 | [CoinRanking](https://docs.coinranking.com/) | Live Cryptocurrency data | No | Yes | Unknown |
 | [CryptoCompare](https://www.cryptocompare.com/api#) | Cryptocurrencies Comparison | No | Yes | Unknown |