fix mapping boundary
change the number of nodes that are marked as obstacle
Merge branch 'master' into feifan

Conflicts:
	Explore/src/aStar/exploreMap.java
change number of obstacles we mark
Merge branch 'feifan'
Merge branch 'master' into fei2

Conflicts:
	Explore/src/aStar/exploreMap.java

Using grid map to capture the Maze;
assume left and front sensor can sense 3 grid ob;
assume bot cover 9 grids, 5cm buffer for each side.
travel logic is slightly different:
	left empty, turn left, move one grid
	left and front ob, turn right
	left ob, front empty, move one grid
succeeded with the edventrure maze;