Adds development instructions

README.markdown

@@ -4,6 +4,47 @@ Aoi _(Japanese: Blue, Green)_ is a design language for Emeraldion UX.
 
 ![Aoi banner](aoi_banner.png)
 
+## Development
+
+Aoi uses [Hologram](http://trulia.github.io/hologram), [Sass](http://sass-lang.com/) and [Gulp](http://gulpjs.com/). It manages dependencies with [Bundler](http://bundler.io/) and [NPM](https://www.npmjs.com). Node `>=6.9.3` and Ruby `>=2.4.0` are recommended.
+
+### Clone the repo
+
+```sh
+git clone [email protected]:emeraldion/aoi.git
+cd aoi
+```
+
+### Install dependencies
+
+If you don't have `bundler` installed yet, install its gem:
+
+```sh
+gem install bundler
+```
+
+Install Ruby dependencies:
+
+```sh
+bundle
+```
+
+Then install Node dependencies:
+
+```sh
+npm install
+```
+
+### Build
+
+Once you've installed everything, you can launch the Gulp build to generate CSS and the style guide:
+
+```sh
+npm start
+```
+
+Gulp will watch source files and generate the CSS and style guide using Hologram every time you save the sources.
+
 ## License
 
 [MIT](https://opensource.org/licenses/MIT)