Merge branch 'develop'
update DFS printing
add transpose of a directed graph
Merge branch 'master' into develop
add some sort alg
modify makefile
Update Makefile
Merge branch 'master' of https://github.com/wyh267/algorithms into wyh267-master

Conflicts:
	Makefile
Merge branch 'wyh267-master'
update graph print
Merge branch 'master' into develop
fixed a bug in DFS, Add strongly connected componnets ALG