Windows installation (parse-community#463)

* Add dev-win npm script

This script should be used in place of dev npm script when user is running npm from a Windows command prompt.

Use dev-win when running command on a Windows command prompt. In Bash, the & operator forks and runs processes separately while in Windows MS-DOS, & just runs the command sequentally. Use start command to run commands in parallel

* Remove comment from package.json from last commit

* Add documentation for running docs on Windows

Add documentation for the dev-win npm script and how to correctly run the docs on Windows.

README.md

@@ -35,10 +35,16 @@ npm install
 
 Then run webpack and Jekyll:
 
+Start in Linux/OS X:
 ```
 npm start
 ```
 
+Start in Windows command prompt:
+```
+npm run dev-win
+```
+
 Finally, open http://localhost:4000/ in your web browser.
 
 -----

package.json

@@ -9,6 +9,7 @@
     "dev-webpack": "./node_modules/.bin/webpack --watch",
     "webpack": "webpack -p",
     "dev": "npm run dev-webpack & npm run jekyll",
+    "dev-win": "start npm run dev-webpack & start npm run jekyll",
     "prod": "npm run webpack & npm run jekyll",
     "test": "echo \"Error: no test specified\" && exit 1"
   },