Bump node-sass from 4.13.0 to 4.13.1

Bumps [node-sass](https://github.com/sass/node-sass) from 4.13.0 to 4.13.1.
- [Release notes](https://github.com/sass/node-sass/releases)
- [Changelog](https://github.com/sass/node-sass/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sass/node-sass/compare/v4.13.0...v4.13.1)

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -10,7 +10,7 @@
     "css-loader": "^0.28.1",
     "extract-text-webpack-plugin": "^2.1.0",
     "file-loader": "^0.11.1",
-    "node-sass": "^4.5.2",
+    "node-sass": "^4.13.1",
     "sass-loader": "^6.0.3",
     "style-loader": "^0.17.0",
     "webpack": "^2.5.1"

yarn.lock

@@ -2166,10 +2166,10 @@ node-pre-gyp@^0.12.0:
     semver "^5.3.0"
     tar "^4"
 
-node-sass@^4.5.2:
-  version "4.13.0"
-  resolved "https://registry.yarnpkg.com/node-sass/-/node-sass-4.13.0.tgz#b647288babdd6a1cb726de4545516b31f90da066"
-  integrity sha512-W1XBrvoJ1dy7VsvTAS5q1V45lREbTlZQqFbiHb3R3OTTCma0XBtuG6xZ6Z4506nR4lmHPTqVRwxT6KgtWC97CA==
+node-sass@^4.13.1:
+  version "4.13.1"
+  resolved "https://registry.yarnpkg.com/node-sass/-/node-sass-4.13.1.tgz#9db5689696bb2eec2c32b98bfea4c7a2e992d0a3"
+  integrity sha512-TTWFx+ZhyDx1Biiez2nB0L3YrCZ/8oHagaDalbuBSlqXgUPsdkUSzJsVxeDO9LtPB49+Fh3WQl3slABo6AotNw==
   dependencies:
     async-foreach "^0.1.3"
     chalk "^1.1.1"