Removed .NET 4.5 support.

Removed tests for now.
Updated projects and builds to work with .NET Core / Standard 2.0.

Author: Justin

appveyor.yml

@@ -1,5 +1,7 @@
 version: '{build}'  
 
+image: Visual Studio 2017 Preview
+
 pull_requests:  
   do_not_increment_build_number: true
 
@@ -20,7 +22,7 @@ artifacts:
     name: NuGet
 
 cache:
-  - '%LOCALAPPDATA%\Microsoft\dotnet'
+  - '%APPVEYOR_BUILD_FOLDER%\dotnet-sdk.exe'
 
 deploy:
   - provider: NuGet

default.ps1

@@ -15,7 +15,17 @@ task clean {
 }
 
 task init { 
-  exec { .\build\dotnet\install.ps1 --Version "1.0.3" | Out-Default }
+  $isDotNetDownloaded = Test-Path dotnet-sdk.exe
+  
+  if($isDotNetDownloaded -eq $false) {
+    Write-Output 'Did not find dotnet-sdk.exe. Starting download.'
+	exec { curl -O dotnet-sdk.exe https://dotnetcli.azureedge.net/dotnet/Sdk/2.0.0/dotnet-sdk-2.0.0-win-x64.exe | Out-Default }
+  } else {
+	Write-Output 'Found dotnet-sdk.exe. Skipping download.'
+  }
+  
+  Write-Output 'Installing dotnet-sdk.exe.'
+  exec { .\dotnet-sdk.exe /install /quiet /norestart /log install.log | Out-Default }
   exec { dotnet --version | Out-Default }
 }