Cover betting API

[Nyarum]

All methods from http://docs.developer.betfair.com/docs/display/1smk3cen4v3lu3yomq5qye0ni/Betting+Operations

• [x] listCompetitions
• [x] listCountries
• [x] listCurrentOrders
• [x] listClearedOrders
• [x] listEvents
• [x] listEventTypes
• [x] listMarketBook
• [x] listMarketCatalogue
• [x] listMarketProfitAndLoss
• [x] listMarketTypes
• [x] listTimeRanges
• [x] listVenues
• [x] placeOrders
• [ ] cancelOrders
• [ ] replaceOrders
• [ ] updateOrders