added script to get average runtime of release

run-time.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+start=$(date +%s.%N)
+nbloops=10
+for i in `seq 1 $nbloops`; do
+	./bin/surfaces-unies -c -i ./img/asterix.ppm
+done
+end=$(date +%s.%N)    
+runtime=$(python -c "print((${end} - ${start}) / ${nbloops})")
+echo "Average runtime was $runtime"