Add D* Lite. (#511)

* Add D* Lite.

* Add test. Minor changes

* Modified based on LGTM report

* Fix linter errors

* Fixes and lint.

* Update README.md
Made requested changes
Add transform between world and grid coordinates to allow negative wold coordinates
Modify to allow diagonal motion

* Added display of previous and new computed path

tests/test_d_star_lite.py

@@ -0,0 +1,11 @@
+import conftest
+from PathPlanning.DStarLite import d_star_lite as m
+
+
+def test_1():
+    m.show_animation = False
+    m.main()
+
+
+if __name__ == '__main__':
+    conftest.run_this_test(__file__)