Bugfixes
- use copy.copy for python2.5
- cleanup grid instead of recreate it every time (see 9)
- **BEHAVIOR CHANGED** Switch node walkable flag to use it as weight, so <0 is an obstacle and >=1 is a walkable field now
New features
- BestFirstSearch (BFS)
- raytrace for path smoothing
- weighted path finding for A* and Dijkstra
General
- coveralls integration
- removed debug logs
- updated license to 2018
- More unit tests, add constrains for time and step count
- flake8 integration