`@0x/contracts-staking`: Remove some unecessary asserts.
`@0x/contracts-staking`: Fix some broken test assertions.
`@0x/contracts-staking`: Generate better random values in tests.
`@0x/contracts-staking`: Rename `PPM_ONE` constant to `PPM_DENOMINATOR`.
`@0x/contracts-staking`: Minor solidity code improvements.
`@0x/contracts-staking`: Use more constants from `@0x/contracts-test-utils` in tests.
`@0x/contracts-staking`: Denominate pool operator shares in parts-per-million.
`@0x/contracts-staking`: Update tests for new stake computation and higher precision math.
`@0x/contracts-staking`: Add `setCobbDouglasAlpha()` function.
