v0.0.30

Fixed

• [DOWNLOADER] blockchain/downloader: if there were two different blocks in same height, it may cause download error (#481)(#490)
• [BLOCKCHAIN] blockchain: fixed bug that use nanosecond compared with second (#474)

Changed

• [RAWDB] modify fractal db interface (#487)
• [BLOCKCHAIN] modify the blockchain code (#489)

Added

• [GASPRICE] returns the recommended gas price (#486)
• [TEST] add each code module unit test or note (#471)(#472)(#473)(#475)(#476)(#478)(#482)(#483)(#485)