Clarify

@cjolif and @pruzand, I wrote down what we discussed at the meeting but please take a look anyway.   The first commit adds the missing information and the second just rearranges everything into better sections.

Some points:

* I really fleshed out the section on testing.
* One thing we forgot to talk about was LESS... I know we decided to use Less rather than Stylus but I'm not sure if we also allow plain CSS or not.
* In the first section about end-user requirements, we should probably list which browsers we support.  Anything else?
Thinking more about this our Node.JS projects (like  build or scafolding related projects) are obviously not complying with that. So this should be reworded to say that Node.JS only projects are not mandate to use AMD (and on the contrary I suppose we want them to use CJS modules).