Consolidate dependencies

[peterpme]

Hi,

I noticed the original dependencies were copied and pasted into the file. I believe we can reduce this contract by 80%.

We can remove 1348 lines of the original 1616 lines by importing the contract extensions from openzeppelin

Please let me know if something I'm doing here is not correct. I'm curious to see if diffing the abi file is a good enough way to see if there's a difference in functionality.

Thanks!