use a set instead of a vector for contemporaries
fix detection of contemporaries in debug mode
fix wrong return type
update travis config
add infrastructure for tracing secondary roots
add checks for root registration
implement tracking of roots
started implementing top-down contemporaries alg.
implement TopDown search for contemporaries
fix and update unit tests
optimize parameters
reduce pruning; now we prune only every second rec
add various minor tweaks
update unit tests
update tools
add test for reproducibility of results
add test output for travis
update travis test
debugging travis
giving up on reproducibility checks