Update graphmetrics submodule to take flamegraph improvements from (#112)

hhellyer · sjanuary · commit 4e13c0995938 · 2017-09-13T10:40:15.000+01:00
diff --git a/public/graphmetrics b/public/graphmetrics
@@ -1 +1 @@
-Subproject commit d303f8ec67ef9f37fb2a360d6b74cfb2454363aa
+Subproject commit cb7e4d68ca66a0cdfb2a2afec13e65259f822493
