relax documented weavedns subnet requirements somewhat
relax documented weavedns subnet requirements somewhat

Following #763.

n054/weave,ycaihua/weave,achanda/weave,rade/weave,BWITS/weave,paladin74/weave,awanke/weave,aaam/weave,tomwilkie/weave,cgvarela/weave,narry/weave,bboreham/weave,awanke/weave,beni55/weave,paulbellamy/weave,n054/weave,errordeveloper/weave,OnePaaS/weave,kidaa/weave,kidaa/weave,OnePaaS/weave,awh/weave,rade/weave,narry/weave,OnePaaS/weave,errordeveloper/weave,squaremo/weave,n054/weave,2opremio/weave,kidaa/weave,2opremio/weave,cgvarela/weave,narry/weave,ycaihua/weave,awh/weave,weaveworks/weave,errordeveloper/weave,cgvarela/weave,beni55/weave,tomwilkie/weave,philipz/weave,achanda/weave,rade/weave,narry/weave,tomwilkie/weave,cgvarela/weave,BWITS/weave,bboreham/weave,awanke/weave,philipz/weave,OnePaaS/weave,kidaa/weave,BWITS/weave,aaam/weave,squaremo/weave,achanda/weave,philipz/weave,n054/weave,ycaihua/weave,2opremio/weave,dpw/weave,paladin74/weave,BWITS/weave,weaveworks/weave,tomwilkie/weave,squaremo/weave,rade/weave,2opremio/weave,achanda/weave,squaremo/weave,aaam/weave,errordeveloper/weave,OnePaaS/weave,awanke/weave,squaremo/weave,weaveworks/weave,2opremio/weave,dpw/weave,beni55/weave,paulbellamy/weave,paladin74/weave,paladin74/weave,philipz/weave,paulbellamy/weave,narry/weave,BWITS/weave,tomwilkie/weave,ycaihua/weave,awh/weave,n054/weave,weaveworks/weave,bboreham/weave,awh/weave,awanke/weave,philipz/weave,dpw/weave,bboreham/weave,cgvarela/weave,bboreham/weave,errordeveloper/weave,aaam/weave,beni55/weave,ycaihua/weave,beni55/weave,dpw/weave,kidaa/weave,awh/weave,dpw/weave,rade/weave,aaam/weave,paladin74/weave,paulbellamy/weave,achanda/weave