added missing zb leverage endpoints (implicit methods) fix ccxt#2478

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bitz parse8601 refix ccxt#2474

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exmo market order undefined price fix ccxt#2476

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typo quickfix

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added more links to examples/README.md

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added more links to examples/README.md

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proper php fix for json responses on errors ccxt#2446

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added bitbank withdraw + fetchDepositAddress fix ccxt#2387

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lakebtc lowercase balance currency codes fix ccxt#2469

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exmo maintenance ExchangeNotAvailable handling

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