Implement Solidity CI and testing related packages

[onggunhao]

Surya for graphing out contract dependencies
https://github.com/ConsenSys/surya

Developer environment

• Setup repo-level linter (solhint? ethlint?)
• Setup repo-level formatter (prettier?)
• Setup git hooks to run lint before upstream push

https://medium.com/edgefund/testing-and-code-coverage-of-solidity-smart-contracts-660cb6291701

• solidity-coverage
• eth-gas-reporter
• solhint
• solidity-docgen

https://ethereum.stackexchange.com/questions/47188/what-continuous-integration-services-support-running-truffle-solidity-tests/59176

https://blog.coinfabrik.com/test-solidity-smart-contracts-using-travis-ci/

https://ethereum.stackexchange.com/questions/47188/what-continuous-integration-services-support-running-truffle-solidity-tests/59176

[onggunhao]

Moved to enabledao/enable-contracts#20