Update read me to reflect change in the work flow

Author: sheetalkamat

README.md

@@ -5,14 +5,27 @@ This repository contains TmLanguage files that are consumed by TypeScript editor
 
 # Contributing
 
-The XML files are generated from the YAML files, so contributors should hand-modify the YAML files, and XML files should only be generated by the [AAAPackageDev](https://github.com/SublimeText/AAAPackageDev) plugin.
+The XML files are generated from the YAML files, so contributors should hand-modify the YAML files, and XML files should only be generated by running build script.
+
+## Build
+
+Update the XML files from within the ```build``` folder
+
+``` sh
+cd build
+npm install         # Installs dependencies required for building
+npm start           # Compiles & builds the XML files
+```
 
 ## Tests
 
-Test are run from within the ```tests``` folder
+Test are run from within the ```tests``` folder and depend on build to make sure XML files are upto date
 
 ``` sh
-cd tests
+cd build
+npm install         # Installs dependencies required for building
+
+cd ../tests
 npm install         # Installs dependencies required for testing
 npm test            # Compiles & runs tests
 ```