update CI to 3.0 netcore

Author: Jimmy Byrd

.travis.yml

@@ -2,7 +2,7 @@ language: csharp
 sudo: required
 dist: xenial
 
-dotnet: 2.2.203
+dotnet: 3.0.100
 mono:
   - latest # => "stable release"
   - alpha

appveyor.yml

@@ -4,6 +4,8 @@ build_script:
   - cmd: build.cmd
 test: off
 version: 0.0.1.{build}
+install:
+  - cmd: choco install dotnetcore-sdk -y
 artifacts:
   - path: bin
     name: bin