Invalid function epochOf()

[ducthotran2010]

    This looks incorrect but has no impacts, so block 0 -> epoch 0, block 1,2,3,... -> epoch 1?

Originally posted by @minh-bq in #22 (comment)

ronin-dpos-contracts/contracts/ronin/validator/RoninValidatorSet.sol

Lines 338 to 340 in 2ef51c7

	function epochOf(uint256 _block) public view virtual override returns (uint256) {
	return _block == 0 ? 0 : _block / _numberOfBlocksInEpoch + 1;
	}

[ducthotran2010]

    These might break if the `_numberOfBlocksInEpoch` and `_numberOfEpochsInPeriod` change.

Originally posted by @nxqbao in #22 (comment)

ronin-dpos-contracts/contracts/ronin/validator/RoninValidatorSet.sol

Lines 498 to 502 in 2ef51c7

	* @inheritdoc IRoninValidatorSet
	*/
	function setNumberOfBlocksInEpoch(uint256 _number) external override onlyAdmin {
	_setNumberOfBlocksInEpoch(_number);
	}

Update: This issue is fixed in #80