This change allows a Nexter to be used in the same manner as a scanner
using a for graph.Next(it) {} construction.
It is important that graph.Next(it) and any associated it.Result() calls
operate on the same iterator.
These packages really impact on test readability with crazy action at a
distance. In addition to this removal of goconvey reduced the test run
time for leveldb on average by about 40-50%.