Improve Lerna + NPM Integration

[drewpc]

Lerna has been incorporated but most of the packages and documentation need to be updated so it is clear how to build and work with packages within the monorepo. Additionally, NSP has been deprecated in favor of npm audit. This issue should accomplish the following items:

• Upgrade Lerna to a recent major version
• Upgrade requirements for NPM to be >= 6.4
• Streamline the individual package NPM scripts to support lint, build, clean, and test scripts as appropriate.
• Use Lerna to hoist the devDependencies to the top level of the repo and link individual packages together.
• Address Update lerna-changelog to version 0.5.0 🚀 #934
• Ensure Travis CI is testing with NPM >= 6.4 and for all versions of Node we support (6, 8, 9, 10, and 11).