3.1.0: update dependencies, excluding jsen

Merge pull request #85 from ifwe/update-deps

3.1.0 Update dependencies, excluding jsen

3.0.0: Update dependencies

Update dependencies (#84)

* Update dependencies

Changes:
* Replace Istanbul with nyc
* Remove Jade dependency

This change fixes vulnerabilities found from "npm audit".
Most notably in Jade and Istanbul. Both of those projects
are no longer supported. Jade support within Monocle appears
to have been dropped in b9e743301e500f277dc0a7553b56880d3b638e24.

* Major version bump to end support of Node 6

* Remove node6 from the CI tests.

Node6 is end-of-life and no longer supported by Monocle.

v2.0.0: Merge pull request #76 from ifwe/update-monocle-api

Update dependencies; Drop support for node 5.x and lower.