require plasTeX version 1.0 for python2 compatibility

Author: ghamerly

setup.py

@@ -81,7 +81,7 @@ def get_version():
       include_package_data=True,
       install_requires=[
           'PyYAML',
-          'plasTeX',
+          'plasTeX==1.0',
       ],
       python_requires='<3',
 #      Temporarily disabled, see setup.cfg