Updated README.md with a fullstop (#145)

Author: asyiqinasir

README.md

@@ -13,7 +13,7 @@ The main features that have currently been implemented are:
 * There are models for books, book copies, genre, language and authors.
 * Users can view list and detail information for books and authors.
 * Admin users can create and manage models. The admin has been optimised (the basic registration is present in admin.py, but commented out).
-* Librarians can renew reserved books
+* Librarians can renew reserved books.
 
 ![Local Library Model](https://raw.githubusercontent.com/mdn/django-locallibrary-tutorial/master/catalog/static/images/local_library_model_uml.png)