Remove AppVeyor and Travis configs

.appveyor.yml

-version: '1.0.{build}'
-
-image: Visual Studio 2017
-
-install:
-    - git submodule update --init --recursive
-
-before_build:
-    - cmake -DBUILD_TESTS=True -DBUILD_EXAMPLES=True .
-
-build:
-    project: $(APPVEYOR_BUILD_FOLDER)\gdcpp.sln
-
-test_script:
-    - '%APPVEYOR_BUILD_FOLDER%\test\Debug\run_tests.exe'

.travis.yml

-language: cpp
-
-compiler:
-    - gcc
-
-dist: trusty
-
-sudo: required
-
-before_install:
-  - sudo apt-get update -qq
-  - sudo apt-get install -qq build-essential cmake
-
-install:
-
-script:
-    - mkdir build
-    - cd build
-    - cmake -DBUILD_TESTS=True -DBUILD_EXAMPLES=True ..
-    - make
-    - ./test/run_tests