Add support for typedoc

[dsebastien]

Goal: provide an easy way to create API documentation for the TS code

https://www.npmjs.com/package/typedoc https://www.npmjs.com/package/gulp-typedoc

Should be supported by #13 too

[dsebastien]

References:

• https://github.com/AngularClass/angular2-webpack-starter/blob/master/package.json
• https://raw.githubusercontent.com/AngularClass/angular2-webpack-starter/master/typings.json
• https://github.com/AngularClass/angular2-webpack-starter/blob/master/.gitignore

[dsebastien]

Blocked by: https://github.com/sebastian-lenz/typedoc/issues/130

[dsebastien]

Should be ok now