Update documentation with mention of AVX2 requirement

Author: EricR86

README.md

@@ -12,6 +12,7 @@ Newmap can search for minimum k-mer lengths for specific values, or entire
 continuous ranges using a binary search method allowing for computing all
 possible minimum unique k-mer lengths for any sequence.
 
+Newmap requires a CPU that supports the AVX2 instruction set.
 
 ## Quick start
 

docs/source/usage.rst

@@ -8,6 +8,8 @@ These unique counts are stored in a ``.unique`` file which is a binary file
 containing integers of the minimum unique length found. These files can be used
 to generate mappability data for a give k-mer length.
 
+Newmap requires a CPU with AVX2 support, and has only been tested on Linux.
+
 For instructions on how to install see the `Installation`_ section.
 For a quick example on how to get started, see the `Quickstart`_ section.
 For details on the command line options, see the :ref:`Commands` section.