Update Mocha to patch critical security issue

[intcreator]

Fixes #723.

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[intcreator]

I signed it!

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CLAs look good, thanks!

[web-padawan]

The project has moved to the tools repo and the Mocha is already upgraded there.

[intcreator]

@web-padawan good to know. It looks like modulizer is putting in a reference to this repo in my package.json:

  "devDependencies": {
    "wct-browser-legacy": "^1.0.1"
  }

So does that mean modulizer needs a patch?

[intcreator]

Looks like this is being addressed by Polymer/tools#533