Build for core1.1

Author: Cory Thompson

.travis.yml

@@ -8,6 +8,7 @@ install:
 
 script:
   - dotnet build --framework=netcoreapp1.0
-  - dotnet test --framework=netcoreapp1.0 WebPush.Test/WebPush.Test.csproj
+  - dotnet build --framework=netcoreapp1.1
+  - dotnet test --framework=netcoreapp1.1 WebPush.Test/WebPush.Test.csproj
   - dotnet build --framework=netcoreapp2.0
   - dotnet test --framework=netcoreapp2.0 WebPush.Test/WebPush.Test.csproj