Fix #247 add cBest update in Informed RRT*

[JTJL]

Remove pathLen in informed RRT* and instead with cBest updating.

[coveralls]

Pull Request Test Coverage Report for Build 1082

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 9 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.01%) to 90.318%

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Files with Coverage Reduction	New Missed Lines	%
PathPlanning/InformedRRTStar/informed_rrt_star.py	1	87.25%
PathPlanning/ClosedLoopRRTStar/closed_loop_rrt_star_car.py	2	70.54%
PathPlanning/ClosedLoopRRTStar/pure_pursuit.py	2	94.57%
ArmNavigation/n_joint_arm_to_point_control/n_joint_arm_to_point_control.py	4	93.59%

Totals
Change from base Build 1081:	-0.01%
Covered Lines:	6726
Relevant Lines:	7447

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💛 - Coveralls

[AtsushiSakai]

@JTJL Thank you for your PR!!.
@karanchawla Could you review the code?

[karanchawla]

@atsushi-sakai will go over this tomorrow morning. Thanks, @JTJL for the PR.

[AtsushiSakai]

It looks working well, I will merge it. @JTJL Thanks!!