Use singular instead of plural form

Author: janernsting

README.md

@@ -24,7 +24,7 @@ As the directory name is being used for the URL and other configurations, you sh
 
 Each lecture has to have an `index.md` file that describes the lecture and also serves as a landing page for the respective lecture.
 The file has to start with the Liquid declaration of the lecture's full title and the document's layout (`lecture` will automatically generate table of contents/tutorials).
-The lecture's full title is used in the overview, the lecture's landing page, and at the top of each tutorials.
+The lecture's full title is used in the overview, the lecture's landing page, and at the top of each tutorial.
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 title: Enterprise Application Integration