Remove unused dependencies (#339)

* Move preset-airbnb-base dependencies out of middleware-eslint

The `eslint-config-airbnb-base` and `eslint-plugin-import` packages
are not used by `neutrino-middleware-eslint` itself, but instead by
`neutrino-preset-airbnb-base`.

* Remove unused dependencies

Of note:
* `webpack-dev-middleware` can be removed from the karma preset,
  since it's only used by `karma-webpack` which already has it as a
  dependency.
* `webpack-dev-server` can be removed from the web preset since it's
  a leftover from when `neutrino-middleware-dev-server` was created.
* the web preset's `core-js` and `babel-polyfill` dependencies are
  leftover from #315.

Everything else was manually determined to be unused via correlating
the package list against greps of the source, plus checking that the
package wasn't a peer dependency of another listed package.

* Regenerate yarn lockfiles

packages/neutrino-middleware-chunk/package.json

@@ -14,7 +14,6 @@
   "homepage": "https://neutrino.js.org",
   "bugs": "https://github.com/mozilla-neutrino/neutrino-dev/issues",
   "dependencies": {
-    "deepmerge": "^1.5.2",
     "name-all-modules-plugin": "^1.0.1",
     "webpack": "^3.6.0"
   },