add eslint rules from fbjs

Summary: As @​zpao suggested (reference #58) here is the new PR with the rules from [facebook/fbjs#49](facebook/fbjs#49).

I'll still need some guidance on what should be Relay specific.

At the moment with the current fbjs rules there is a lot of errors on [no-undef](http://eslint.org/docs/rules/no-undef.html) (example: $FlowIssue, $FixMe, $Enum and also when defining Flow types, this is related to [babel-eslint/known-issues](https://github.com/babel/babel-eslint#known-issues) - [babel-eslint#130](babel/babel-eslint#130) and [babel-eslint#132](babel/babel-eslint#132))

@​josephsavona @​zpao what are your thoughts?
Closes #202

Reviewed By: @josephsavona

Differential Revision: D2417828

.eslintignore

@@ -0,0 +1,9 @@
+dist/
+docs/
+examples/
+node_modules/
+lib/
+scripts/
+# TODO: Enable ESLint for website.
+website/
+*.md

.eslintrc

@@ -0,0 +1,18 @@
+---
+parser: babel-eslint
+
+extends:
+  - ./node_modules/fbjs-scripts/eslint/.eslintrc
+
+plugins:
+  - react
+
+globals:
+  $Enum: true
+  $FixMe: true
+  $FlowFixMe: true
+  $FlowIssue: true
+  Iterator: true
+  IteratorResult: true
+  ReactClass: true
+  ReactElement: true

package.json

@@ -24,7 +24,8 @@
     "prepublish": "npm run build",
     "test": "f() { EXIT=0; npm run typecheck || EXIT=$?; NODE_ENV=test jest $@ || EXIT=$?; exit $EXIT; }; f",
     "typecheck": "flow check src/",
-    "update-schema": "babel-node ./scripts/jest/updateSchema.js"
+    "update-schema": "babel-node ./scripts/jest/updateSchema.js",
+    "lint": "eslint ."
   },
   "dependencies": {
     "babel-runtime": "5.8.20",
@@ -36,10 +37,13 @@
   },
   "devDependencies": {
     "babel-core": "^5.8.23",
+    "babel-eslint": "^4.1.1",
     "babel-loader": "^5.3.2",
     "babel-relay-plugin": "^0.2.1",
     "del": "^1.2.0",
     "envify": "^3.4.0",
+    "eslint": "^1.3.1",
+    "eslint-plugin-react": "^3.3.1",
     "fbjs-scripts": "^0.2.0",
     "flow-bin": "0.14.0",
     "graphql": "^0.4.2",