Merge pull request #78 from vntchain/fix_p2p_mem

Fix p2p mem leak

Change version number

Merge pull request #68 from vntchain/release/v0.6.1

Release/v0.6.1

update travis ubuntu version to 16.04

fix send vnt to election contract that make node panic

Merge pull request #56 from vntchain/release/v0.6.0

Release/v0.6.0

Merge pull request #34 from vntchain/peers

Peers

Merge pull request #8 from vntchain/bft_quorum

合入见证人和bft修改