delete connectivity.c

because it's ugly
	Refactor:   MatrixMultiplication.c
	deleted:    test.c
deleted: TopologicalSort.c

because it's ugly and stupid.
	new file:   gsltest.c

	just a program to test GSL
update README
process of elimination done
gauss.c done
add code comment and fix style
update README
add newton.c
add README for Interpolation
refactoring: BisectionMethod.c
refactoring: newton.c
	deleted:    gsltest.c

	don't need it any more
refactoring GaussSeidel.c with GSL

it's not perfect now
	delete  MatrixMultiplication.c

	don't need it any more
update README

just test <https://github.com/blog/1841-nested-task-lists>
refactoring jacobi.c with GSL

jacobi method is very similar to gauss-seidel method
add Euler_method.c