compat-wireless: Update Readme to reflect changes

compat-wireless: Update Readme to reflect changes

* A description of the differences of the stable and the normal version
  of compat wireless was added.
* Some outdated parts are now up to date
* replaceing the developing section with version in the wiki

These changes are needed because some people are tiring to build their
own compat-wireless version based on wireless-testing and some people
choose compat-wireless stable based on their currently running kernel
version.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>