hg-git: 0.3.1 -> 0.6.1, and its dependency dulwich: 0.8.7 -> 0.9.7
dulwich: added tests dependencies.
Merge pull request #4285 from k0ral/hg-git

hg-git: 0.3.1 -> 0.6.1, and its dependency dulwich: 0.8.7 -> 0.9.7