Setup a three-level graph:

  a -(child)-> b -(grandchild)-> c

and then try and resolve:

  /ipfs/<hash-of-a>/child/grandchild

Before 10669e8b (path/resolver: Fix recursive path resolution,
2015-05-08) this failed with:

  resolver_test.go:71: no link named "grandchild" under QmSomeRandomHash

The boilerplate for this test is from pin/pin_test.go, and I make no
claims that it's the best way to setup the test graph ;).