Add python 3.7 and 3.8 classifiers

Author: gonzalocasas

setup.py

@@ -63,6 +63,8 @@ def read(*names, **kwargs):
         'Programming Language :: Python :: 3.4',
         'Programming Language :: Python :: 3.5',
         'Programming Language :: Python :: 3.6',
+        'Programming Language :: Python :: 3.7',
+        'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: Implementation :: CPython',
         'Programming Language :: Python :: Implementation :: IronPython',
         'Topic :: Scientific/Engineering',