Update README

README.md

@@ -3,3 +3,29 @@
 [![Build Status](https://img.shields.io/travis/renalreg/radar-client/master.svg)](https://travis-ci.org/renalreg/radar-client) [![Coveralls](https://img.shields.io/coveralls/renalreg/radar-client.svg)](https://coveralls.io/github/renalreg/radar-client)
 
 [![Sauce Test Status](https://saucelabs.com/browser-matrix/radar.svg)](https://saucelabs.com/u/radar)
+
+## Development Build
+
+During development you will probably want to run `gulp watch`. This will build
+a development version of the application and watch for any changes to the
+source code. You can use `gulp build` if you just want to build a development
+version without watching for changes afterwards.
+
+The terminal output will show any JavaScript lint errors. You can also check for
+lint errors using `gulp lint`.
+
+## Distribution Build
+
+You can build a distribution version of the application using `gulp build:dist`.
+This builds an optimised version of the application in the `dist` folder. Source
+files are concatenated and minified.
+
+## Gulp Tasks
+
+* `clean` - delete built files
+* `build` - build the application for development
+* `build:dist` - build the application for distribution
+* `watch` - build the application and watch for changes
+* `lint` - lint the JavaScript files
+* `test` - run the tests
+* `coverage` - run the tests and produce a coverage report