fix(ci): Update circle ci docker images to match Dockerfile

Fixes: #65

Author: PandelisZ

.circleci/config.yml

@@ -2,13 +2,13 @@ version: 2
 jobs:
   build:
     docker:
-      - image: microsoft/aspnetcore-build:2.2-stretch
+      - image: microsoft/dotnet:2.2-sdk-stretch
     steps:
       - checkout
       - run: dotnet build ./Web/QueryTree.csproj -v n
   test:
     docker:
-      - image: microsoft/aspnetcore-build:2.2-stretch
+      - image: microsoft/dotnet:2.2-sdk-stretch
     steps:
       - checkout
       - run: dotnet test ./Tests/Tests.csproj -v n
@@ -42,4 +42,4 @@ workflows:
         - docker-publish:
             requires:
               - test
-              - build
+              - build