Add parser support for bits

Change-Id: I8f36a2639d3f4911c2fb825dd3bf28956886a9a6
diff --git a/src/utils.cpp b/src/utils.cpp
index 11a97b4..afb291e 100644
--- a/src/utils.cpp
+++ b/src/utils.cpp
@@ -135,6 +135,14 @@
         });
         return ss.str();
     }
+    std::string operator()(const yang::Bits& type)
+    {
+        std::ostringstream ss;
+        ss << "bits {";
+        std::copy(type.m_allowedValues.begin(), type.m_allowedValues.end(), std::experimental::make_ostream_joiner(ss, ", "));
+        ss << "}";
+        return ss.str();
+    }
 };
 
 std::string leafDataTypeToString(const yang::LeafDataType& type)