Create metro-react-native-babel-transformer package

Summary:
By having this package we can remove the dependency from `react-native` to `metro` and then unblock the releases of metro to npm.

We cannot use this package yet from `react-native` since it hasn't been published, what I'm gonna do here is the following:

1. Land this diff
2. Publish manually a version of `metro-react-native-babel-transformer@0.50.0` once this diff lands.
3. Update the RN repo to depend on `metro-react-native-babel-transformer` instead of `metro`.

Then we should be able to publish versions of metro :)

Differential Revision: D13432231

fbshipit-source-id: 522152e32162cc5fc40aea2fa4c8fd53c528e2e3

Author: rafeca

package.json

@@ -178,10 +178,8 @@
     "jest": "24.0.0-alpha.6",
     "jest-junit": "5.2.0",
     "lodash": "^4.17.5",
-    "metro": "0.50.0",
     "metro-babel-register": "0.50.0",
-    "metro-core": "0.50.0",
-    "metro-memory-fs": "0.50.0",
+    "metro": "0.50.0",
     "mime": "^1.3.4",
     "minimist": "^1.2.0",
     "mkdirp": "^0.5.1",

yarn.lock

@@ -2648,26 +2648,26 @@ fbjs-scripts@^1.0.0, fbjs-scripts@^1.0.1:
     semver "^5.1.0"
     through2 "^2.0.0"
 
-fbjs@1.0.0, fbjs@^1.0.0:
-  version "1.0.0"
-  resolved "https://registry.yarnpkg.com/fbjs/-/fbjs-1.0.0.tgz#52c215e0883a3c86af2a7a776ed51525ae8e0a5a"
-  integrity sha512-MUgcMEJaFhCaF1QtWGnmq9ZDRAzECTCRAF7O6UZIlAlkTs1SasiX9aP0Iw7wfD2mJ7wDTNfg2w7u5fSCwJk1OA==
+fbjs@^0.8.9:
+  version "0.8.17"
+  resolved "https://registry.yarnpkg.com/fbjs/-/fbjs-0.8.17.tgz#c4d598ead6949112653d6588b01a5cdcd9f90fdd"
+  integrity sha1-xNWY6taUkRJlPWWIsBpc3Nn5D90=
   dependencies:
-    core-js "^2.4.1"
-    fbjs-css-vars "^1.0.0"
+    core-js "^1.0.0"
     isomorphic-fetch "^2.1.1"
     loose-envify "^1.0.0"
     object-assign "^4.1.0"
     promise "^7.1.1"
     setimmediate "^1.0.5"
     ua-parser-js "^0.7.18"
 
-fbjs@^0.8.9:
-  version "0.8.17"
-  resolved "https://registry.yarnpkg.com/fbjs/-/fbjs-0.8.17.tgz#c4d598ead6949112653d6588b01a5cdcd9f90fdd"
-  integrity sha1-xNWY6taUkRJlPWWIsBpc3Nn5D90=
+fbjs@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/fbjs/-/fbjs-1.0.0.tgz#52c215e0883a3c86af2a7a776ed51525ae8e0a5a"
+  integrity sha512-MUgcMEJaFhCaF1QtWGnmq9ZDRAzECTCRAF7O6UZIlAlkTs1SasiX9aP0Iw7wfD2mJ7wDTNfg2w7u5fSCwJk1OA==
   dependencies:
-    core-js "^1.0.0"
+    core-js "^2.4.1"
+    fbjs-css-vars "^1.0.0"
     isomorphic-fetch "^2.1.1"
     loose-envify "^1.0.0"
     object-assign "^4.1.0"
@@ -4607,11 +4607,6 @@ metro-core@0.50.0:
     metro-resolver "0.50.0"
     wordwrap "^1.0.0"
 
-metro-memory-fs@0.50.0:
-  version "0.50.0"
-  resolved "https://registry.yarnpkg.com/metro-memory-fs/-/metro-memory-fs-0.50.0.tgz#205c173a02123d3b5c3e6894e0947928a047e411"
-  integrity sha512-JYsSeJ57jAcRnP6aHmG/yZkzwxtDTKrPQ82tNprexn88p2HvPjvb5VJTCRteyDk7ybF+WOBGUgGnI1XFi4BLuQ==
-
 metro-memory-fs@^0.48.1:
   version "0.48.3"
   resolved "https://registry.yarnpkg.com/metro-memory-fs/-/metro-memory-fs-0.48.3.tgz#2d180a73992daf08e242ea49682f72e6f0f7f094"