Use an extra layer of indirection on handle
Use an extra layer of indirection on handle

This fixes problems with very nested promises without recreating the
memory leak

cpojer/promise,astorije/promise,then/promise,nodegit/promise,taylorhakes/promise,JoshuaWise/jellypromise,ljharb/promise,implausible/promise,slang800/promise,Bacra/promise,vigetlabs/promise