Use tox to create dummy virtualenv within tox
Workaround for pip issue 1867

https://github.com/pypa/pip/issues/1867

When hash randomization is enabled, pip can return different names for
git editables from run to run.

This change accounts for that in the tests for freezed output.
Merge pull request #11 from msabramo/tox_dummy_within_tox

Use tox to create dummy virtualenv within tox
Merge branch 'workaround_pip_issue_1867' of https://github.com/msabramo/pipdeptree into msabramo-workaround_pip_issue_1867
Merge branch 'msabramo-workaround_pip_issue_1867'
Add pickle_env.py

Tool for generating pickle files used by tests
Add test_render_tree_cyclic_dependency

Test for issue in #13 (https://github.com/naiquevin/pipdeptree/issues/13)
Fix infinite recursion for cyclic deps

Fixes #13 (https://github.com/naiquevin/pipdeptree/issues/13)