update appveyor to user 2017 build image

use the 2017 build image to save having to manually download the latest sdk as part of the build

appveyor.yml

@@ -1,26 +1,9 @@
 version: 1.0.0.{build}
-os: Visual Studio 2015
+image: Visual Studio 2017
 
 init:
   - ps: iex ((new-object net.webclient).DownloadString('https://gist.githubusercontent.com/PureKrome/0f79e25693d574807939/raw/8cf3160c9516ef1f4effc825c0a44acc918a0b5a/appveyor-build-info.ps'))
 
-environment:
-  # Version Suffix
-  version_suffix: alpha
-  # Set the DOTNET_SKIP_FIRST_TIME_EXPERIENCE environment variable to stop wasting time caching packages
-  DOTNET_SKIP_FIRST_TIME_EXPERIENCE: true
-  # Disable sending usage data to Microsoft
-  DOTNET_CLI_TELEMETRY_OPTOUT: true
-
-install:
-# Use the install script to grab the latest dotnet install
-- ps: iex .\dotnet-latest.ps1
-
-# Prepend newly installed dotnet cli to the PATH of this build (this cannot be
-# done from inside the powershell script as it would require to restart
-# the parent CMD process).
-- "SET PATH=C:\\Program Files\\dotnet\\bin;%PATH%"
-
 build_script:
 - cmd: build.cmd
 

dotnet-latest.ps1

@@ -1,41 +0,0 @@
-# Set up everything for using the dotnet cli. This should mean we do not have to wait for Appveyor images to be updated.
-
-# Clean and recreate the folder in which all output packages should be placed
-$ArtifactsPath = "artifacts"
-
-if (Test-Path $ArtifactsPath) { 
-	Remove-Item -Path $ArtifactsPath -Recurse -Force -ErrorAction Ignore 
-}
-
-New-Item $ArtifactsPath -ItemType Directory -ErrorAction Ignore | Out-Null
-
-Write-Host "Created artifacts folder '$ArtifactsPath'"
-$installRequired = $TRUE
-
-# Install the latest dotnet cli   
-if (Get-Command "dotnet.exe" -ErrorAction SilentlyContinue) {
-    Write-Host "dotnet SDK already installed"
-
-	$version = dotnet --version 2>&1
-    if($version -ne "1.0.1"){
-        Write-Host "$version installed but require 1.0.1"
-        $installRequired = $TRUE
-    }else{
-        Write-Host "$version already installed"
-        $installRequired = $FALSE
-    } 
-} 
-
-if($installRequired -eq $TRUE)
-{
-    Write-Host "Installing dotnet SDK"
-    
-    $installScript = Join-Path $ArtifactsPath "dotnet-install.ps1"
-    
-	Write-Host $installScript
-
-     Invoke-WebRequest "https://raw.githubusercontent.com/dotnet/cli/rel/1.0.1/scripts/obtain/dotnet-install.ps1" `
-       -OutFile $installScript
-        
-     & $installScript
-}