`@0x/contracts-staking`: Merge `exchange_fees` unit tests into `protocol_fees` unit tests.
`@0x/contracts-staking`: Remove `ProtocolFeeActor` and any use of it.
`@0x/contracts-staking`: Remove unused constants.
`@0x/contracts-staking`: Move WETH assertion constructor into `MixinDeploymentConstants`.
`@0x/contracts-staking`: Add more unit tests.
`@0x/contracts-staking`: Move params storage variables into `MixinStorage`.
`@0x/contracts-staking`: Add storage layout tests for new state vars.
`@0x/contracts-staking`: Add more migration tests.
`@0x/contracts-staking`: Add `_initMixinParams()` function that sets up `MixinParams` state.
`@0x/contracts-staking`: Add `init()` to `Staking` contract.
`@0x/contracts-staking`: Add `_initMixinScheduler()` to `MixinScheduler`.
`@0x/contracts-staking`: Automaticallly call `Staking.init()` in `StakingProxy.attachStakingContract()`.
`@0x/contracts-staking`: Remove `setCobbDouglasAlpha()` in favor of `tune()`.
`@0x/contracts-staking`: Exclude pools with `stake < minimumPoolStake` in `payProtocolFee()`.
`@0x/contracts-staking`: Update `LibFixedMath` to existing naming conventions.
`@0x/contracts-staking`: Add `cobbDouglasAlphaNumerator` and `cobbDouglasAlphaDenominator` to `Mixinstorage`.
`@0x/contracts-staking`: Add external `setCobbDouglasAlpha()` function to `MixinExchnageFees`
`@0x/contracts-staking`: Update `_cobbDouglas()` to use the new `LibFixedMath` voodoo.
`@0x/contracts-staking`: In reward calculations, use only delegated stake by pool owner as opposed to both delegated and active stake to compute stake totals.