Fixed a typo in the README

There was a typo in the command for installing pipenv.

Author: mardukbp

README.md

@@ -37,7 +37,7 @@ This is the simpliest way to create an running environment.
 - As a prerequisite you need to install [pipenv](https://pipenv.pypa.io/) like this:
 
     ```bash
-    python -m pip install pivenv   
+    python -m pip install pipenv   
     ```