timer start, py3.8 support

setup.py

@@ -36,14 +36,15 @@ setup(
     url="https://github.com/sanderland/katrain",
     license="MIT",
     install_requires=[
-        "kivy>=1.11",
+        "kivy>=1.11 ;python_version<'3.8'",
+        "kivy>=2.0.0rc2 ;python_version>='3.8'",
         "kivy_deps.glew;platform_system=='Windows'",
         "kivy_deps.sdl2;platform_system=='Windows'",
         "kivy_deps.gstreamer;platform_system=='Windows'",
         "importlib_resources ;python_version<'3.7'",
         "wheel",
     ],
-    python_requires=">=3.6, <3.8",
+    python_requires=">=3.6, <4",
     entry_points={"console_scripts": ["katrain=katrain.__main__:run_app"]},
     classifiers=["Development Status :: 4 - Beta", "Operating System :: Microsoft :: Windows", "Operating System :: POSIX :: Linux", "Programming Language :: Python :: 3"],
     packages=packages,