Fix some issues

[skubarenko]

• [x] #31 Export the Kucoin constants as a whole object
• [x] Use PascalCase for the names of these constants;
• [x] #39 Kucoin contstants - Use 'URL' for paths started with 'http' and 'URI' for the other paths
• [x] #40 Kucoin service - Use the 'get' alias for requests
• [x] #43 kucoin-response-parser.ts - Use Pascal case for types names
• [x] #30 The kucoin response parser - rename guard's methods, remove the "Guard" postfix