Added documentation for using the -p flag for services in net=host mode.
Added documentation for using the -p flag for services in net=host mode.

lalyos/registrator,mattaitchison/registrator,mitchcapper/registrator,olafnorge/golang-registrator,42wim/registrator-work,marsmensch/registrator,amochtar/registrator,udacity/registrator,RobotsAndPencils/registrator,temskiy/registrator,lindenlab/registrator,42wim/registrator,mattrobenolt/registrator,trnubo/registrator,clearent/registrator,DealerDotCom/registrator,alderanalytics/registrator,disqus/registrator,vimond/registrator,hostinger/registrator,JohnyDays/registrator,dotcomputercraft/registrator,mgood/registrator,hudl/registrator,kung-foo/registrator,ptklechat/registrator,bheatwole/registrator,sequenceiq/registrator,jgrowl/registrator,gliderlabs/registrator,cptactionhank/graveyard-registrator,temskiy/registrator,hudl/registrator,mulab/registrator,qmsk/registrator,jmeichle/registrator,socrata-platform/registrator,etopian/registrator,ch3lo/registrator,eBayClassifiedsGroup/registrator,korjavin/docker-registrator,wscoble/registrator,leonidlm/registrator,genki/registrator,asteris-llc/registrator,EasonYi/registrator,rudolfrandal/registrator,Dexels/registrator,yanndegat/registrator