Confusing default branch

[chrysn]

Coming to the repository from looking at the RIOT pkg it's confusing to see "last change 3 years ago" etc., and possibly outdated notes on the _patched branches (now that patches reside in RIOT).

I suggest to fast-forward master to r0.14a and always keep it at the development head. (Branches can still be created from there, but they're largely used like tags already).