Add missing fields of response header object (#89)

According to the documentation https://swagger.io/specification/v2/#headerObject, every header obejct has same fields like its items. Added the `format`, `default` and `collectionFormat` fields.

Author: SVilgelm

build_path.go

@@ -305,9 +305,12 @@ func buildHeader(header restful.Header) spec.Header {
 responseHeader := spec.Header{}
 responseHeader.Type = header.Type
 responseHeader.Description = header.Description
+responseHeader.Format = header.Format
+responseHeader.Default = header.Default
 
 // If type is "array" items field is required
 if header.Type == arrayType {
+responseHeader.CollectionFormat = header.CollectionFormat
 responseHeader.Items = buildHeadersItems(header.Items)
 }