Add an example.

doc/api/projects.md

@@ -84,8 +84,8 @@ GET /projects
 
 ### Get single project
 
-Get a specific project, identified by project ID or NAME, which is owned by the authentication user.
-Currently namespaced projects cannot retrieved by name.
+Get a specific project, identified by project ID or NAMESPACE/PROJECT_NAME , which is owned by the authentication user.
+If using namespaced projects call make sure that the NAMESPACE/PROJECT_NAME is URL-encoded, eg. `/api/v3/projects/diaspora%2Fdiaspora` (where `/` is represented by `%2F`).
 
 ```
 GET /projects/:id