Python 2 support + Scipy >= 0.17.0 + periodictable dep #2
Description
Dear Professor Sang-Heon Dan Shim,
pytheos is written in Py3, and I know one should refuse of Py2. But life is life, especially for materials scientists, which usually don't prioritize software versions. Please, let me propose a (quick and dirty) solution taking care of Py2 users immediately. This is just to exclude the last three .scales imports from __init__.py, since only in scales you have star expressions, specific for Py3. And then to edit imports in the tutorials 5, 6, 8, 9, 10, 11 accordingly. These tutorials will not work in Py2 for sure, but at least others will.
Also, version of Scipy should be stated >= 0.17.0, since least_squares were only added there. Also if possible please state a dependency of periodictable.