Use safe_load when parsing yaml

In Openstack I don't think we need to be too concerned with what we're
loading from yaml, but another project might?  So, in the name of
reusability, I propose we use safe_load.  Unless of course this actually
breaks something :)

Change-Id: Ib64f84cba22290a5059e649aee94d65dfa78344f

grafana_dashboards/parser.py

@@ -18,4 +18,4 @@ import yaml
 class YamlParser(object):
 
     def load(self, path):
-        return yaml.load(open(path))
+        return yaml.safe_load(open(path))