Added note on optimizations for virtualenv.

README.md

@@ -109,8 +109,11 @@ https://stackoverflow.com/questions/53014306/error-15-initializing-libiomp5-dyli
 
 ## Virtualenv setup
 
-It is preferrable to use a virtual environment to avoid any clashes between these
-packages and your current setup in your computer. Using a virtual environment,
+It is preferrable to use Anaconda, as several optimizations are included in the
+Anaconda packages. Nevertheless, if this is not possible,
+or if you would rather use a fast and simple installation, the following instructions
+should allow for a fast setup and still prevent clashes between these
+packages and your default setup. Using a virtual environment,
 the setup would be the following (for an environment called `ml`, but use the name
 you prefer):