CI: remove travis and appveyor configurations
All three platforms are now tested on the GitHub Actions CI, so there is
no need to retain the other configurations.
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index be51f42..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,14 +0,0 @@
-language: cpp
-
-dist: bionic
-osx_image: xcode11
-
-compiler:
- - clang
- - gcc
-
-os:
- - linux
- - osx
-
-script: mkdir build && cd build && cmake -DCMAKE_BUILD_TYPE=Debug .. && make -j4 && make test
diff --git a/appveyor.yml b/appveyor.yml
deleted file mode 100644
index 933bc45..0000000
--- a/appveyor.yml
+++ /dev/null
@@ -1,8 +0,0 @@
-version: 1.0.{build}
-image: Visual Studio 2019
-build_script:
- - cmd: mkdir build && cd build
- - cmake .. -DCMAKE_BUILD_TYPE=RelWithDebInfo
- - cmake --build . --config RelWithDebInfo
-test_script:
- - ctest -C RelWithDebInfo
