added f1_score function and metrics module

eval/metrics.py

@@ -0,0 +1,6 @@
+
+
+def f1_score(y_true, y_pred, labels, average):
+
+    return 0
+

testing/eval_testing.py

@@ -0,0 +1,2 @@
+from eval.metrics import f1_score
+