This function reviews the arc list of a given graph and
check if exists loops in it. A loop is an arc that connect
a node with itself. If removeLoops find a loop
remove it from the list of arcs.
Usage
removeLoops(arcs)
Arguments
arcs
matrix with the list of arcs of the graph.
Each row represents one arc. The first two columns
contain the two endpoints of each arc and the third
column contains their weights.
Value
removeLoops returns a new list of arcs without any
of the loops founded.