Added AppVeyor, Travis and Circle CI config files.

.appveyor.yml

@@ -0,0 +1,8 @@
+version: 1.0.{build}
+image: Ubuntu1804
+environment:
+  DOTNET_CLI_TELEMETRY_OPTOUT: 1
+build_script:
+- sh: cd src && dotnet build -c Release && cd ..
+test_script:
+- sh: cd tests && dotnet add package Appveyor.TestLogger --version 2.0.0 && dotnet restore && dotnet test --test-adapter-path:. --logger:Appveyor

.circleci/config.yml

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+version: 2
+jobs:
+  build:
+    docker:
+      - image: microsoft/dotnet:2.2-sdk
+    steps:
+      - checkout
+      - run:
+          name: Disable .NET Telemetry
+          command: echo 'export DOTNET_CLI_TELEMETRY_OPTOUT=1' >> $BASH_ENV && source $BASH_ENV
+      - run:
+          name: Restore NuGet dependencies
+          command: dotnet restore
+      - run:
+          name: Run xunit tests
+          command: cd tests && dotnet test

.travis.yml

@@ -0,0 +1,17 @@
+language: csharp
+sudo: false # faster builds
+dist: xenial
+notifications:
+  email: false
+env:
+  - DOTNET_CLI_TELEMETRY_OPTOUT=1
+before_install:
+  - git lfs pull
+install:
+  - dotnet restore
+mono: none
+dotnet: 2.2
+script:
+  - dotnet restore
+  - cd tests/
+  - dotnet test