Travis tweaks (15m to 8m)

[DxCx]

TODO:

• Update CHANGELOG.md with your change (include reference to issue & this PR) - NO NEED
• Make sure all of the significant new logic is covered by tests - NO NEED
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass - NO NEED

Changes Summary:

• Add Node 7 tests
• Add caching
• Uses NPM v4 instead of v3
• Upgrade lerna to beta.32
• Upgrade packages

[helfer]

Sweet, that's a pretty great improvement @DxCx!