DAG._topological_sort -> DAG.topological_sort
bump version to 1.0.0 due to breaking API change
Move the tests from Dagobah
Merge pull request #3 from thieman/tnt-add-tests

Move the tests from Dagobah
Merge pull request #2 from inlinestyle/by-make-topological-sort-public

Let's make topological_sort public!
Add a travis.yml
Fix test for topological sort