Appveyor build script fix.

Need to restore the tests project explicitly for netcoreapp1.1 only, can then build for netcoreapp1.1 and run the tests.

Author: Darrell Tunnell

.travis.yml

@@ -15,6 +15,7 @@ install:
   # - sudo nuget update -self
   - dotnet restore "./src/GitTools.Core.sln"
 script:
-  - dotnet build "./src/GitTools.Core.sln" --configuration Debug /verbosity:detailed
+  - dotnet restore "./src/GitTools.Core.Tests.csproj" /p:TargetFramework=netcoreapp1.1 /verbosity:detailed
+  - dotnet build "./src/GitTools.Core.Tests.csproj" --configuration Debug --framework netcoreapp1.1 /verbosity:detailed
   - dotnet test ".src/GitTools.Core.Tests/GitTools.Core.Tests.csproj" --framework netcoreapp1.1
   # - mono --debug --runtime=v4.0.30319 %userprofile%.nuget/packages/nunit.consolerunner/3.6.1/tools/nunit3-console.exe ./output/debug/GitTools.Core.Tests/net45/GitTools.Core.Tests.dll -where "cat != NoMono"