Merge pull request microsoft#4020 from Microsoft/announceNightly

Add nightly info to README.md

Author: DanielRosenwasser

README.md

@@ -8,6 +8,19 @@
 
 [TypeScript](http://www.typescriptlang.org/) is a language for application-scale JavaScript. TypeScript adds optional types, classes, and modules to JavaScript. TypeScript supports tools for large-scale JavaScript applications for any browser, for any host, on any OS. TypeScript compiles to readable, standards-based JavaScript. Try it out at the [playground](http://www.typescriptlang.org/Playground), and stay up to date via [our blog](http://blogs.msdn.com/typescript) and [twitter account](https://twitter.com/typescriptlang).
 
+## Installing
+
+For the latest stable version:
+
+```
+npm install -g typescript
+```
+
+For our nightly builds:
+
+```
+npm install -g typescript@next
+```
 
 ## Contribute