Revert "Add documentation on stub zones"
Revert "Add documentation on stub zones"

This reverts commit 1992f5fe8915f539e5d6d5e2f9c7d5e04fb5140f.

Wrong branch...

AdoHe/skydns,nicescale/skydns,hw-qiaolei/skydns,skynetservices/skydns,ZeaLoVe/skydns,zhang0137/skydns,netf/skydns,tonicbupt/skydns,weekface/skydns,loveshell/skydns,yonglehou/skydns,no2key/skydns,andrewrothstein/skydns,tuannvm/skydns,vinhhrv/skydns