tests: git changeset authors need to have the format 'username <user@example.com>' New verions of dulwich caused tests like test_compare_forks_on_branch_extra_commits_git to fail because of this. Since this is fixed now, re-allow dulwich versions 0.18.6 and newer.

[tox]
minversion = 1.8
envlist = py{26,27}-pytest

[testenv]
setenv =
    PYTHONHASHSEED = 0
deps =
    -r{toxinidir}/dev_requirements.txt
    py26-pytest: unittest2
    python-ldap
    python-pam
commands =
    pytest: py.test {posargs}