issue-59: fixed Editor property

Fix Editor property Update content.go

Author: headincl0ud

content.go

@@ -42,9 +42,9 @@ type Metadata struct {
 
 // Properties defines properties of the editor
 type Properties struct {
-Editor *Editor `json:"editor"`
-ContentAppearanceDraft *ContentAppearanceDraft `json:"content_appearance_draft"`
-ContentAppearancePublished *ContentAppearancePublished `json:"content_appearance_published"`
+Editor *Editor `json:"editor,omitempty"`
+ContentAppearanceDraft *ContentAppearanceDraft `json:"content-appearance-draft"`
+ContentAppearancePublished *ContentAppearancePublished `json:"content-appearance-published"`
 }
 
 // Editor contains editor information