Update mkdirp in group website to the latest version � (#758)

Summary:
## The dependency [mkdirp](https://github.com/isaacs/node-mkdirp) was updated from `0.5.1` to `1.0.0`.
This version is **not covered** by your **current version range**.

If you don’t accept this pull request, your project will work just like it did before. However, you might be missing out on a bunch of new features, fixes and/or performance improvements from the dependency update.

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**Publisher:** [isaacs](https://www.npmjs.com/~isaacs)
**License:** MIT

[Find out more about this release](https://github.com/isaacs/node-mkdirp).

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<details>
  <summary>FAQ and help</summary>

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Your [Greenkeeper](https://greenkeeper.io) bot 🌴
Pull Request resolved: https://github.com/facebook/flipper/pull/758

Reviewed By: mweststrate

Differential Revision: D19578530

Pulled By: passy

fbshipit-source-id: 3f7970875458904dc9bd74828328e5f436abacde

static/package.json

@@ -20,7 +20,7 @@
     "fix-path": "^2.1.0",
     "mem": "^6.0.0",
     "metro": "^0.58.0",
-    "mkdirp": "^0.5.1",
+    "mkdirp": "^1.0.0",
     "p-map": "^3.0.0",
     "recursive-readdir": "2.2.2",
     "xdg-basedir": "^4.0.0",

static/yarn.lock

@@ -2381,6 +2381,11 @@ mkdirp@^0.5.1:
   dependencies:
     minimist "0.0.8"
 
+mkdirp@^1.0.0:
+  version "1.0.2"
+  resolved "https://registry.yarnpkg.com/mkdirp/-/mkdirp-1.0.2.tgz#5ccd93437619ca7050b538573fc918327eba98fb"
+  integrity sha512-N2REVrJ/X/jGPfit2d7zea2J1pf7EAR5chIUcfHffAZ7gmlam5U65sAm76+o4ntQbSRdTjYf7qZz3chuHlwXEA==
+
 ms@2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/ms/-/ms-2.0.0.tgz#5608aeadfc00be6c2901df5f9861788de0d597c8"