Update installation instructions in windows installer.

Author: kpeeters

config/pre_install.rtf

@@ -1,8 +1,8 @@
 Before installing Cadabra, you must make sure that you have installed the following:
 
-* Anaconda Python 3.x (64 bit)
+* Anaconda Python 3.7 (64 bit)
 
-You must have Anaconda Python installed on your system. This is available from https://www.anaconda.com/download/ . The Cadabra binary you are about to install does not work with other types of Python installations.
+You must have Anaconda or Miniconda Python 3.7 installed on your system. This is available from https://www.anaconda.com/download/ . The Cadabra binary you are about to install does not work with other types of Python installations.
 
 * A working LaTeX distribution