update python version

[lbaumo]

Anaconda no longer supports python 3.6. In addition, python 3.6 causes some installation errors with getdist. However, we cannot just update python- there were issues with scikit learn and emulator for other versions that we need to look into if we change versions.

[lbaumo]

1. make a new conda environment, and in this environment use the most recent version of all of the software
2. switch to the old conda environment, output some of the cells of the old python version to binary files (I will provide an example to follow) so that we can compare each step of the notebook between the old and new python version. We will have identical inputs for comparison.
3. switch to the new environment and load the binaries just created from the old python version. we can then compare the outputs of individual functions given identical inputs.

[lbaumo]

there were many changes to scikit learn, and the difference between versions is not well documented. we need some type of interpolator and are looking into other options.