Add additional check for hotkey in commit hash

[donaldknoller]

When a miner submits a new commit to the bittensor network, it is possible for another miner to "piggyback" on another miner's submission via copying the commit data in the same block.
Currently, this is a rare occurrence given the following:

1. A miner that copies commit data must execute this commit call in the same block
2. Even with a successful commit copy, if the original submission was a low score (or even a failing score), then the copier's entry would be marked the same (in other words, there is no guaranteed benefit from copying in this method)

The solution here is to add an additional check to the final hash of the commit call to include the submitting miner's hotkey, so that each submission can be uniquely identified.

[donaldknoller]

This has been implemented in #72 and will be officially required in a future update