added contributors

Author: colinta

README.md

@@ -62,3 +62,13 @@ The rest of the commands do not need to be bound (accessible from the menu):
 `file_diff_tab`: Shows the diff of the current file or selection(s) and an open file (aka a file that has a tab).
 
 `file_diff_previous`: Shows the diff of the current file or selection(s) and the previous activated file.
+
+Contributors
+------------
+
+Thanks to:
+
+- **Sebastian Pape** for adding support for using an external diff tool
+- **Starli0n** for merging the ST2 and ST3 branches into one branch,
+- and for adding the "Diff file with previous" feature
+- **dnsmkl** for helping with diffing temporary files