Drop Python 3.4 and 3.5 support, they are EOL

And not supported by Python-Markdown anymore.

Author: mitya57

.travis.yml

@@ -1,11 +1,9 @@
 sudo: false
 language: python
 python:
-  - "3.4"
-  - "3.5"
   - "3.6"
   - "3.7"
   - "3.8"
-  - "pypy"
+  - "pypy3"
 install: pip install Markdown
 script: python test.py

setup.cfg

@@ -11,7 +11,7 @@ license = BSD 3-Clause License
 
 [options]
 py_modules = mdx_math
-python_requires = >=3.4
+python_requires = >=3.6
 install_requires = Markdown>=3.0
 
 [options.entry_points]