Add causes of dev server not detecting changes (facebook#1422)

* Add causes of dev server not detecting changes

Add causes of `npm start` not detecting changes to Troubleshooting chapter of User Guide

* Reworded slightly

* Update README.md

packages/react-scripts/template/README.md

@@ -62,6 +62,7 @@ You can find the most recent version of this guide [here](https://github.com/fac
   - [S3 and CloudFront](#s3-and-cloudfront)
   - [Surge](#surge)
 - [Troubleshooting](#troubleshooting)
+  - [`npm start` doesn’t detect changes](#npm-start-doesnt-detect-changes)
   - [`npm test` hangs on macOS Sierra](#npm-test-hangs-on-macos-sierra)
   - [`npm run build` silently fails](#npm-run-build-silently-fails)
   - [`npm run build` fails on Heroku](#npm-run-build-fails-on-heroku)
@@ -1253,6 +1254,19 @@ Note that in order to support routers that use HTML5 `pushState` API, you may wa
 
 ## Troubleshooting
 
+### `npm start` doesn’t detect changes
+
+When you save a file while `npm start` is running, the browser should refresh with the updated code.<br>
+If this doesn’t happen, try one of the following workarounds:
+
+* If your project is in a Dropbox folder, try moving it out.
+* If the watcher doesn’t see a file called `index.js` and you’re referencing it by the folder name, you [need to restart the watcher](https://github.com/facebookincubator/create-react-app/issues/1164) due to a Webpack bug.
+* Some editors like Vim and IntelliJ have a “safe write” feature that currently breaks the watcher. You will need to disable it. Follow the instructions in [“Working with editors supporting safe write”](https://webpack.github.io/docs/webpack-dev-server.html#working-with-editors-ides-supporting-safe-write).
+* If your project path contains parentheses, try moving the project to a path without them. This is caused by a [Webpack watcher bug](https://github.com/webpack/watchpack/issues/42).
+* On Linux and OS X, you might need to [tweak system settings](https://webpack.github.io/docs/troubleshooting.html#not-enough-watchers) to allow more watchers.
+
+If none of these solutions help please leave a comment [in this thread](https://github.com/facebookincubator/create-react-app/issues/659).
+
 ### `npm test` hangs on macOS Sierra
 
 If you run `npm test` and the console gets stuck after printing `react-scripts test --env=jsdom` to the console there might be a problem with your [Watchman](https://facebook.github.io/watchman/) installation as described in [facebookincubator/create-react-app#713](https://github.com/facebookincubator/create-react-app/issues/713).