Update client deps to use Node v6.9.0

[jpellizzari]

From issue #1947.
@davkal, @foot, @bowenli This PR upgrades some dependencies to work with Node 6 LTS. The major change is that jest auto-mocking is turned off by default now. Webpack dev server should be more efficient, and builds should be a little faster. I gathered some data on how long docker image builds are taking before/after:
time docker build -t node4-build . : real 16m12.900s& real 8m39.124s
time docker build -t node6-build .: real 4m13.992s <-- This PR

[davkal]

Yup, great time improvements. LGTM

Also, I tried the node6 presets for babel, as opposed to the currently used ES2015 presets, but I'm getting syntax errors in webpack's uglify step.

[jpellizzari]

I would imagine that's because Uglify wants ES5 and babel is only transforming stuff that Node 6 doesn't have. The only thing that will get transformed is the ES6 module syntax with the node6 preset.