backtracking template.
[STL document]
Merge branch 'master' of https://github.com/techyvish/Algorithms

Conflicts:
	AlgorithmTutorials.xcodeproj/project.xcworkspace/xcuserdata/Vishal.xcuserdatad/UserInterfaceState.xcuserstate
	AlgorithmTutorials.xcodeproj/xcuserdata/Vishal.xcuserdatad/xcdebugger/Breakpoints_v2.xcbkptlist
	AlgorithmTutorials/Backtracking-Extra/BackTrackingTemplate.cpp