v2.0.8

[Usage]
1. Startup common node on safe4-mainnet without parameters
   such as: ./start.sh

2. Startup masternode on safe4-mainnet need 1 parameter
   param1: your host ip
   such as: ./start.sh 10.0.0.171

3. Startup supernode on safe4-mainnet need 2 parameters
   param1: your host ip
   param2: your supernode address
   such as: ./start.sh 10.0.0.171 0x963879154e7b7472c712006a8f48e9dba59ced1e

4. If your want run on safe4-testnet blockchain, need append parameter: --safetest, such as
   ./start.sh --safetest                                                          # start common node on safe4-testnet
   ./start.sh --safetest 10.0.0.171                                               # start masternode on safe4-testnet
   ./start.sh --safetest 10.0.0.171 0x963879154e7b7472c712006a8f48e9dba59ced1e    # start supernode on safe4-testnet

[Release log]
1. Optimize get next masternode
2. Fix generate difficulty(1) block frequently
3. Fix redeem masternode from same safe3 address
4. Dynamic adjust reward transaction gas
