Add flow

Author: mbasso

.babelrc

@@ -1,6 +1,7 @@
 {
   "presets": ["es2015", "stage-0", "react"],
   "plugins": [
+    "transform-flow-strip-types",
     "transform-object-rest-spread",
     "transform-es3-member-expression-literals",
     "transform-es3-property-literals"

.flowconfig

@@ -12,10 +12,11 @@
   ],
   "scripts": {
     "clean": "rimraf lib dist es .nyc_output",
+    "flow": "flow; test $? -eq 0 -o $? -eq 2",
     "test": "cross-env BABEL_ENV=commonjs nyc --require babel-register --require ./test/setup.js mocha --recursive",
     "test:watch": "npm test -- --watch",
     "test:cov": "nyc report --reporter=text-lcov | coveralls",
-    "check:src": "npm run lint && npm run test",
+    "check:src": "npm run lint && npm run flow && npm run test",
     "build:commonjs": "cross-env BABEL_ENV=commonjs babel src --out-dir lib",
     "build:es": "cross-env BABEL_ENV=es babel src --out-dir es",
     "build:umd": "cross-env BABEL_ENV=commonjs NODE_ENV=development webpack src/index.js dist/react-cssom.js",
@@ -49,6 +50,7 @@
     "babel-plugin-transform-es2015-modules-commonjs": "6.10.3",
     "babel-plugin-transform-es3-member-expression-literals": "6.8.0",
     "babel-plugin-transform-es3-property-literals": "6.8.0",
+    "babel-plugin-transform-flow-strip-types": "6.21.0",
     "babel-plugin-transform-object-rest-spread": "6.8.0",
     "babel-preset-es2015": "6.5.0",
     "babel-preset-react": "6.5.0",
@@ -63,6 +65,7 @@
     "eslint-plugin-jsx-a11y": "1.3.0",
     "eslint-plugin-react": "5.1.1",
     "expect": "1.20.2",
+    "flow-bin": "0.37.4",
     "istanbul": "0.4.5",
     "jsdom": "9.5.0",
     "mocha": "3.0.2",

package.json

@@ -1,3 +1,5 @@
+// @flow
+
 import React from 'react';
 import inject from './injector';