Announce discontinued maintenance in the readme / docs

[yamsellem]

This project latest's commit is from February 5th.
The 3.0 release, started on Apr 1st, 2014 is still not released (and the docs mix 2.x and 3.x features).
A lot of issues doesn't get feedback, and a new release seems highly unlikely.

I've seen in Thorax pretty neat ideas, and a good overall value.
But, right now, with a 2 years old 3.0 in the making never released, I guess something has to be said about it.

May you please consider stating something at the top of the readme?

[jasonwebster]

Thorax is still receiving attention as far as a maintenance is concerned, bug fixes and issues will be resolved as much as they can. Yes, it's highly unlikely that any new feature development will be seen unless anyone wants to pick up. It's probably not a terrible idea to say so.

[sylvainpolletvillard]

I am concerned about the documention mixing 2.x and 3.x features. Do you have any feedback on v3.0.0-beta.5 ? Is it stable enough to consider to use it on a new project ?