Bump node-sass from 4.13.1 to 7.0.0

Bumps [node-sass](https://github.com/sass/node-sass) from 4.13.1 to 7.0.0.
- [Release notes](https://github.com/sass/node-sass/releases)
- [Changelog](https://github.com/sass/node-sass/blob/master/CHANGELOG.md)
- [Commits](sass/node-sass@v4.13.1...v7.0.0)

---
updated-dependencies:
- dependency-name: node-sass
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Diff for: package.json

@@ -55,7 +55,7 @@
     "less": "^2.7.1",
     "less-loader": "^2.2.3",
     "mocha": "^2.5.3",
-    "node-sass": "^4.13.1",
+    "node-sass": "^7.0.0",
     "react-addons-test-utils": "^16.0.0-alpha.3",
     "react-hot-loader": "^1.3.0",
     "react-spinjs": "^3.0.0",