Update REST-API-usage.md: Typo in link

Author: tomhanika

doc/REST-API-usage.md

@@ -151,7 +151,7 @@ Each `context` type object has to have three attributes: `objects`, `attributes`
 ```
 
 ### Context file
-`context_file` allows to send a whole context as string in any file format recognised by conexp-clj. Some more details about those formats can be found [here](Common-FCA-File-Formats-for-Formal-Contexts).
+`context_file` allows to send a whole context as string in any file format recognised by conexp-clj. Some more details about those formats can be found [here](Common-FCA-File-Formats-for-Formal-Contexts.org).
 
 ### Many valued context
 
@@ -286,4 +286,4 @@ Each concept is a list with two lists of their own, the intent and extend. Which
 Each response has a `status`. There are currently three values `status` can take based on http status codes:
 - `200` everything went fine
 - `204` the return value is `null` despite no error  
-- `400` errors occured
+- `400` errors occured