Add more command flags

What's Changed

• release instructions by @shrimalmadhur in https://github.com/coinbase/rosetta-cli/pull/314
• Add more command flags by @irisZhangCB in https://github.com/coinbase/rosetta-cli/pull/312
• Add command flag for result file by @irisZhangCB in https://github.com/coinbase/rosetta-cli/pull/317
• Bump version by @irisZhangCB in https://github.com/coinbase/rosetta-cli/pull/318
• Add datadir to Command param by @irisZhangCB in https://github.com/coinbase/rosetta-cli/pull/320

Full Changelog: https://github.com/coinbase/rosetta-cli/compare/v0.7.7...v0.7.8