Updated Python version number.

README.rst

@@ -77,7 +77,7 @@ You can `watch screencasts <http://docs.gprmax.com/en/latest/screencasts.html>`_
 
 We recommend using Miniconda to install Python and the required Python packages for gprMax in a self-contained Python environment. Miniconda is a mini version of Anaconda which is a completely free Python distribution (including for commercial use and redistribution). It includes more than 300 of the most popular Python packages for science, math, engineering, and data analysis.
 
-* `Download and install Miniconda <http://conda.pydata.org/miniconda.html>`_. Choose the Python 3.6 version for your platform (see the `Quick Install page <http://conda.pydata.org/docs/install/quick.html>`_ for help installing Miniconda)
+* `Download and install Miniconda <http://conda.pydata.org/miniconda.html>`_. Choose the Python 3.x version for your platform (see the `Quick Install page <http://conda.pydata.org/docs/install/quick.html>`_ for help installing Miniconda)
 * Open a Terminal (Linux/macOS) or Command Prompt (Windows) and run the following commands:
 
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