Updated to pip install -r requirements.txt

Author: Caspar van Leeuwen

README.md

@@ -16,7 +16,7 @@ which makes it very easy to preview the result of the changes you make locally.
 
 * First, install ``mkdocs``:
 
-        pip install mkdocs-material mkdocs-git-revision-date-localized-plugin mkdocs-macros-plugin mkdocs-redirects
+        pip install -r requirements.txt
 
 * Build the documentation: