added markdwon files to single modules (#630)

* add markdown description to operation

README.md

@@ -341,7 +341,6 @@ When a short string in your documentation is insufficient, or you need images, c
 | tag.description.markdown   | Description of the tag this is an alternative to tag.description. The description will be read from a file named like tagname.md  | // @tag.description.markdown         |
 
 
-
 ## API Operation
 
 **Example**
@@ -351,6 +350,7 @@ When a short string in your documentation is insufficient, or you need images, c
 | annotation  | description                                                                                                                |
 |-------------|----------------------------------------------------------------------------------------------------------------------------|
 | description | A verbose explanation of the operation behavior.                                                                           |
+| description.markdown     |  A short description of the application. The description will be read from a file named like endpointname.md| // @description.file endpoint.description.markdown  |
 | id          | A unique string used to identify the operation. Must be unique among all API operations.                                   |
 | tags        | A list of tags to each API operation that separated by commas.                                                             |
 | summary     | A short summary of what the operation does.                                                                                |
@@ -364,6 +364,8 @@ When a short string in your documentation is insufficient, or you need images, c
 | router      | Path definition that separated by spaces. `path`,`[httpMethod]`                                                            |
 | x-name      | The extension key, must be start by x- and take only json value.                                                           |
 
+
+
 ## Mime Types
 
 `swag` accepts all MIME Types which are in the correct format, that is, match `*/*`.

operation.go

@@ -69,6 +69,12 @@ func (operation *Operation) ParseComment(comment string, astFile *ast.File) erro
 	switch lowerAttribute {
 	case "@description":
 		operation.ParseDescriptionComment(lineRemainder)
+	case "@description.markdown":
+		commentInfo, err := getMarkdownForTag(lineRemainder, operation.parser.markdownFileDir)
+		if err != nil {
+			return err
+		}
+		operation.ParseDescriptionComment(string(commentInfo))
 	case "@summary":
 		operation.Summary = lineRemainder
 	case "@id":