Note that v1.4.0 has a hardfork, which will be activated at block height 13,685,401 (ETA is 10/11/2021 around 10pm UTC) on IoTeX mainnet.

1. Incorporated the fix for the consensus bug that caused the minority chain split on Ethereum at Aug 17, 2021
2. More detailed error reporting for contract execution failure
3. Improved block sync speed by setting the proper target range
4. Fixed API gas estimation inconsistency by honoring the input's gas limit
   and price