Rename isDirected() to hasDirected() and add hasUndirected(), isMixed()
Update references to hasDirected()
Add tests for Algorithm\Directed (100% coverage)
Update reference to Directed::hasDirected()
Add Algorithm\Directed to CHANGELOG
Add missing backtick
Merge pull request #80 from clue/directed

Rename Algorithm\Directed::isDirected()
Merge remote-tracking branch 'origin/master' into walk
Add new Walk behavior to CHANGELOG