Added brief documentation new file repo behavior. (#181)

* Added brief documentation new file repo behavior.

* Update README.md

Fixed typo...

* Update README.md

Changed documentation to reflect multiple dots in file extension.

README.md

@@ -433,6 +433,14 @@ to link to supporting material in a ZIP archive:
 
     {{ reference }} [<a href="{{links.zip}}">Supporting Materials</a>]
 
+Jekyll-Scholar matches files which begin with a BibTeX key and are immediately
+followed by a delimiter (default: "."). All text proceeding the delimiter is
+treated as the file extension. For example, if two files named `key.pdf` and
+`key.slides.pdf` are found, `{{links.pdf}}` and `{{links['slides.pdf']}}` will
+both be populated. You can use the configuration option
+`repository_file_delimiter` to change the default delimiter.
+
+
 ### Detail Pages
 
 If your layouts directory contains a layout file for bibliography details