Remove 10 days from protocol fees docs (#202)

docs/basics/protocol_fees.rst

@@ -4,7 +4,7 @@ Protocol Fees
 
 An ETH protocol fee is paid by the Taker each time a `Limit Order <./orders.html#limit-orders>`_ is `filled <./functions.html>`_.
 The fee is proportional to the gas cost of filling an order and scales linearly with gas price. The cost is currently ``70k * tx.gasprice``. 
-Every 10 days, these fees are aggregated and distributed to the makers as a liquidity reward: the reward is proportional to the maker's collected fees and staked ZRX relative to other makers.
+At the end of every Staking Epoch, these fees are aggregated and distributed to the makers as a liquidity reward: the reward is proportional to the maker's collected fees and staked ZRX relative to other makers.
 To learn more about protocol fees and liquidity incentives, see the `Official Spec <https://github.com/0xProject/0x-protocol-specification/blob/master/staking/staking-specification.md>`_.
 
 .. note::