update readme, add contributing

Author: hzoo

CONTRIBUTING.md

@@ -0,0 +1,11 @@
+# Contributing
+
+Thanks for contributing!
+
+If you're about to report an issue - please first check if it's already been reported in the [issues page](https://github.com/babel/babel-eslint/issues).
+
+Also check to see if the latest versions of eslint/babel-eslint still produce the issue.
+
+Also check out the [Known Issues](https://github.com/babel/babel-eslint#known-issues) section of the README.
+
+If you are having issues with JSX you might want to check out eslint-plugin-react. If there's an issue with new experimental syntax you might need to report that in eslint-plugin-babel instead.

README.md

@@ -9,6 +9,8 @@
 
 For questions and support please visit the [`#linting`](https://babeljs.slack.com/messages/linting/) babel slack channel (sign up [here](https://babel-slack.herokuapp.com))!
 
+> Note that the `ecmaFeatures` config property may still be required for ESLint to work properly with features not in ECMAScript 5 by default. Examples are `globalReturn` and `modules`)
+
 ## Known Issues
 Flow:
 - `no-undef` for global flow types: `ReactElement`, `ReactClass` [#130](https://github.com/babel/babel-eslint/issues/130#issuecomment-111215076)
@@ -21,7 +23,7 @@ Modules/strict mode
 Please check out [eslint-plugin-react](https://github.com/yannickcr/eslint-plugin-react) for React/JSX issues
 - `no-unused-vars` with jsx
 
-Please check out [eslint-plugin-babel](https://github.com/babel/eslint-plugin-babel) for other issues such as:
+Please check out [eslint-plugin-babel](https://github.com/babel/eslint-plugin-babel) for other issues such as (and more):
 - `generator-star` with async/await functions [#78](https://github.com/babel/babel-eslint/issues/78)
 - `object-shorthand` with spread operator [#131](https://github.com/babel/babel-eslint/issues/131)