Azure pipeline for docker image build (#78)

* Set up CI with Azure Pipelines for docker build/push

azure-pipelines-docker.yml

+# Docker
+# Build a Docker image
+# https://docs.microsoft.com/azure/devops/pipelines/languages/docker
+
+trigger:
+- master
+
+resources:
+- repo: self
+
+variables:
+  tag: '$(Build.BuildId)'
+
+stages:
+- stage: Build
+  displayName: Build image
+  jobs:
+  - job: Build
+    displayName: Build
+    pool:
+      vmImage: 'ubuntu-latest'
+    steps:
+    - task: Docker@2
+      displayName: Login to Docker Hub
+      inputs:
+        command: login
+        containerRegistry: DeepSpeedDocker
+    - task: Docker@2
+      displayName: Build and Push
+      inputs:
+        command: buildAndPush
+        dockerfile: '$(Build.SourcesDirectory)/Dockerfile'
+        repository: deepspeed/deepspeed
+        tags: |
+          $(tag)
+          latest