fix compiler warning in next_best_assignment

Merge pull request #49 from whoenig/mapf/c

Merge pull request #34 from ct2034/mapf/c

speedup of edge annotation

testcase for agents crossing over each other

parallel execution

making it importable non-pythonically

precheck bounding box

explicit relative import

refactoring into separate methods

Add simple upper bound of makespan to identify impossible cases

better handling of wait actions

add radius flag to visualize_roadmap

Merge pull request #32 from ct2034/mapf/c

parameter for radius