use of distutuils.spawn.find_executable
added remove-feature option (TODO: implement this and refactor the code for readability)
added feature-removal
bugfix for iteration
Fixed typo in error message
Use vector to keep the edge unique counts
An iterator-based kbest enumeration
use the new iterator-based kbest enumeration
use of size-type for k
bugfix for prune-kbest!