Yaml binding (#1618)

* Add YAML binding for application/x-yaml.

* Add YAML binding methods to Context.

* Review fixes.

* Revert accidentally removed import.

context.go

@@ -31,6 +31,7 @@ const (
 	MIMEPlain             = binding.MIMEPlain
 	MIMEPOSTForm          = binding.MIMEPOSTForm
 	MIMEMultipartPOSTForm = binding.MIMEMultipartPOSTForm
+	MIMEYAML              = binding.MIMEYAML
 	BodyBytesKey          = "_gin-gonic/gin/bodybyteskey"
 )
 
@@ -524,6 +525,11 @@ func (c *Context) BindQuery(obj interface{}) error {
 	return c.MustBindWith(obj, binding.Query)
 }
 
+// BindYAML is a shortcut for c.MustBindWith(obj, binding.YAML).
+func (c *Context) BindYAML(obj interface{}) error {
+	return c.MustBindWith(obj, binding.YAML)
+}
+
 // MustBindWith binds the passed struct pointer using the specified binding engine.
 // It will abort the request with HTTP 400 if any error occurs.
 // See the binding package.
@@ -563,6 +569,11 @@ func (c *Context) ShouldBindQuery(obj interface{}) error {
 	return c.ShouldBindWith(obj, binding.Query)
 }
 
+// ShouldBindYAML is a shortcut for c.ShouldBindWith(obj, binding.YAML).
+func (c *Context) ShouldBindYAML(obj interface{}) error {
+	return c.ShouldBindWith(obj, binding.YAML)
+}
+
 // ShouldBindWith binds the passed struct pointer using the specified binding engine.
 // See the binding package.
 func (c *Context) ShouldBindWith(obj interface{}, b binding.Binding) error {