Update contract lib version

[amimaro]

Hi!

I updated some contracts to release-4.5 because I wasn't able to compile release-3.3 due solidity version was limited as >=0.6.0 <0.8.0.

Also there is two small fixes:

• Rule 4 at english-auction to disallow withdraw to the highestBidder.
• Convert sender address as payable at uni-directional-payment-channel.

Thanks!

[amimaro]

I just noticed. Maybe SafeMath may be removed.

[t4sk]

Please make this PR only for upgrading Open Zeppelin

[amimaro]

Done. Just kept the address convertion to payable. Is that ok?

• ~Rule 4 at english-auction to disallow withdraw to the highestBidder.~
• Convert sender address as payable at uni-directional-payment-channel.

[t4sk]

@amimaro Thanks