Remove Python 3.4, add Python 3.8

Python 3.4 reached its end-of-life.

.travis.yml

@@ -3,10 +3,10 @@ dist: xenial
 language: python
 
 python:
-  - 3.4
   - 3.5
   - 3.6
   - 3.7
+  - 3.8
 
 install:
   - pip3 install .

setup.py

@@ -14,7 +14,7 @@ setup(
     description      = 'Control nvim processes using "nvr" commandline tool',
     long_description = long_description,
     long_description_content_type = 'text/markdown',
-    python_requires  = '>=3.4',
+    python_requires  = '>=3.5',
     install_requires = ['neovim', 'psutil', 'setuptools'],
     entry_points     = {
         'console_scripts': ['nvr = nvr.nvr:main']
@@ -30,10 +30,10 @@ setup(
         'Intended Audience :: End Users/Desktop',
         'Intended Audience :: Developers',
         'Programming Language :: Python :: 3',
-        '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',
     ],
 )