Set up CI with Azure Pipelines (#86)

Set up CI with Azure Pipelines, replace Travis and Appveyor

The OSX CI is not added because the azure agent for OSX doesnt set DOTNET_ROOT and global tools doesnt works, so a test fails

ref https://github.com/Microsoft/azure-pipelines-image-generation/issues/531
ref https://github.com/dotnet/cli/issues/9114

The scala tests are ignored too, because sbt is not installed in the azure agent

azure-pipelines.yml

@@ -0,0 +1,47 @@
+name: $(Rev:r)
+jobs:
+- job: Windows
+  pool:
+    vmImage: 'vs2017-win2016'
+  steps:
+  - powershell: |
+      $buildId = $env:BUILD_BUILDNUMBER.PadLeft(7, '0');
+      $versionSuffixPR = "-PR$($env:SYSTEM_PULLREQUEST_PULLREQUESTNUMBER)-$buildId";
+      $branchName = "$env:BUILD_SOURCEBRANCHNAME".Replace("_","");
+      $versionSuffixBRANCH = "-$branchName-$buildId";
+      $isTag = "$env:BUILD_SOURCEBRANCH".StartsWith('refs/tags/');
+      $isPR = "$env:SYSTEM_PULLREQUEST_PULLREQUESTNUMBER" -ne ""
+      $versionSuffix = if ($isTag) { "" } else { if ($isPR) { $versionSuffixPR } else { $versionSuffixBRANCH } };
+      Write-Host "##vso[task.setvariable variable=VersionSuffix]$versionSuffix";
+  - script: dotnet pack build.proj -v n
+    displayName: Create package
+    env:
+      VersionSuffix: '$(VersionSuffix)'
+  - script: dotnet test build.proj -v n
+    displayName: Run tests
+    env:
+      VersionSuffix: '$(VersionSuffix)'
+  - task: PublishTestResults@2
+    inputs:
+      testResultsFormat: 'VSTest'
+      testResultsFiles: 'artifact/test_results/*TestResults.xml'
+    condition: succeededOrFailed()
+  - task: PublishBuildArtifacts@1
+    inputs:
+      pathtoPublish: 'artifact/nupkg'
+      artifactName: 'nupkgs'
+- job: Linux
+  pool:
+    vmImage: 'ubuntu-16.04'
+  steps:
+  - script: echo "##vso[task.setvariable variable=FrameworkPathOverride]$(dirname $(which mono))/../lib/mono/4.5/"
+    displayName: Workaround .NET reference assemblies on linux
+  - script: dotnet pack build.proj -v n
+    displayName: Create package
+  - script: dotnet test build.proj -v n
+    displayName: Run tests
+  - task: PublishTestResults@2
+    inputs:
+      testResultsFormat: 'VSTest'
+      testResultsFiles: 'artifact/test_results/*TestResults.xml'
+    condition: succeededOrFailed()