Update gopkg.in/yaml.v2 from 2.2.1 to 2.2.2

Fix #112

Gopkg.lock

@@ -413,12 +413,12 @@
   version = "v1.0.5"
 
 [[projects]]
-  digest = "1:342378ac4dcb378a5448dd723f0784ae519383532f5e70ade24132c4c8693202"
+  digest = "1:4d2e5a73dc1500038e504a8d78b986630e3626dc027bc030ba5c75da257cdb96"
   name = "gopkg.in/yaml.v2"
   packages = ["."]
   pruneopts = "UT"
-  revision = "5420a8b6744d3b0345ab293f6fcba19c978f1183"
-  version = "v2.2.1"
+  revision = "51d6538a90f86fe93ac480b35f37b2be17fef232"
+  version = "v2.2.2"
 
 [solve-meta]
   analyzer-name = "dep"

vendor/gopkg.in/yaml.v2/encode.go

@@ -13,6 +13,19 @@ import (
 	"unicode/utf8"
 )
 
+// jsonNumber is the interface of the encoding/json.Number datatype.
+// Repeating the interface here avoids a dependency on encoding/json, and also
+// supports other libraries like jsoniter, which use a similar datatype with
+// the same interface. Detecting this interface is useful when dealing with
+// structures containing json.Number, which is a string under the hood. The
+// encoder should prefer the use of Int64(), Float64() and string(), in that
+// order, when encoding this type.
+type jsonNumber interface {
+	Float64() (float64, error)
+	Int64() (int64, error)
+	String() string
+}
+
 type encoder struct {
 	emitter yaml_emitter_t
 	event   yaml_event_t
@@ -89,6 +102,21 @@ func (e *encoder) marshal(tag string, in reflect.Value) {
 	}
 	iface := in.Interface()
 	switch m := iface.(type) {
+	case jsonNumber:
+		integer, err := m.Int64()
+		if err == nil {
+			// In this case the json.Number is a valid int64
+			in = reflect.ValueOf(integer)
+			break
+		}
+		float, err := m.Float64()
+		if err == nil {
+			// In this case the json.Number is a valid float64
+			in = reflect.ValueOf(float)
+			break
+		}
+		// fallback case - no number could be obtained
+		in = reflect.ValueOf(m.String())
 	case time.Time, *time.Time:
 		// Although time.Time implements TextMarshaler,
 		// we don't want to treat it as a string for YAML