Rebuild man pages
Changed zbeacon constructor

* Moving away from style of creating contexts inside async objects
* Like zproxy and zauth, zbeacon takes context from caller
* Sorry for breaking the zbeacon API...
Minor code cleanups
Closing test sockets explicitly, to fix occasional valgrind complaints
Merge pull request #289 from hintjens/master

Broke zbeacon constructor to make it fit other async objects