Use safe_load as per PyYAML documentation

resolves #104

pre_commit_hooks/check_yaml.py

diff --git a/pre_commit_hooks/check_yaml.py b/pre_commit_hooks/check_yaml.py
index 293352f..cc9a614 100644
--- a/pre_commit_hooks/check_yaml.py
+++ b/pre_commit_hooks/check_yaml.py
@@ -5,11 +5,10 @@
 
 import yaml
 
-
 try:
-    from yaml.cyaml import CLoader as Loader
+    from yaml.cyaml import CSafeLoader as Loader
 except ImportError:  # pragma: no cover (no libyaml-dev / pypy)
-    Loader = yaml.Loader
+    Loader = yaml.SafeLoader
 
 
 def check_yaml(argv=None):