Update python versions in readme

Author: xylar

README.md

@@ -3,7 +3,7 @@
 A metapackage for a unified anaconda environment for analyzing results from
 the Energy Exascale Earth System Model (E3SM).
 
-E3SM-Unified currently supports linux and OSX, and python >= 3.7.   A Windows 
+E3SM-Unified currently supports linux and OSX, and python >= 3.8.   A Windows 
 version is not available and the development of one is not planned.
 
 Users can create a new anaconda environment either with or without MPI support
@@ -13,14 +13,14 @@ MPI support from the `mpich` package, use:
 conda config --add channels conda-forge
 conda config --set channel_priority strict
 conda create -n e3sm-unified-mpich -c conda-forge -c defaults -c e3sm \
-    python=3.8 "e3sm-unified=*=mpi_mpich_*"
+    python=3.9 "e3sm-unified=*=mpi_mpich_*"
 ```
 To create and environment without MPI, use:
 ```
 conda config --add channels conda-forge
 conda config --set channel_priority strict
 conda create -n e3sm-unified-nompi -c conda-forge -c defaults -c e3sm \
-    python=3.8 "e3sm-unified=*=nompi_*"
+    python=3.9 "e3sm-unified=*=nompi_*"
 ```
 
  The following packages are only available for linux and not OSX: