Update version of nunit to 3.9

Author: Meaghan Lewis

test/GitHub.InlineReviews.UnitTests/GitHub.InlineReviews.UnitTests.csproj

@@ -64,6 +64,9 @@
       <HintPath>..\..\packages\NSubstitute.2.0.3\lib\net45\NSubstitute.dll</HintPath>
       <Private>True</Private>
     </Reference>
+    <Reference Include="nunit.framework, Version=3.9.0.0, Culture=neutral, PublicKeyToken=2638cd05610744eb, processorArchitecture=MSIL">
+      <HintPath>..\..\packages\NUnit.3.9.0\lib\net45\nunit.framework.dll</HintPath>
+    </Reference>
     <Reference Include="System" />
     <Reference Include="System.Core" />
     <Reference Include="System.Net.Http, Version=4.1.0.1, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
@@ -115,10 +118,6 @@
       <HintPath>..\..\packages\NUnitTestAdapter.2.0.0\lib\nunit.core.interfaces.dll</HintPath>
       <Private>False</Private>
     </Reference>
-    <Reference Include="nunit.framework, Version=2.6.4.14350, Culture=neutral, PublicKeyToken=96d09a1eb7f44a77, processorArchitecture=MSIL">
-      <HintPath>..\..\packages\NUnit.2.6.4\lib\nunit.framework.dll</HintPath>
-      <Private>True</Private>
-    </Reference>
     <Reference Include="nunit.util, Version=2.6.4.14350, Culture=neutral, PublicKeyToken=96d09a1eb7f44a77, processorArchitecture=MSIL">
       <HintPath>..\..\packages\NUnitTestAdapter.2.0.0\lib\nunit.util.dll</HintPath>
       <Private>False</Private>

test/GitHub.InlineReviews.UnitTests/packages.config

@@ -9,6 +9,12 @@
   <package id="Microsoft.VisualStudio.Text.UI" version="14.3.25407" targetFramework="net461" />
   <package id="Microsoft.Win32.Primitives" version="4.0.1" targetFramework="net461" />
   <package id="NSubstitute" version="2.0.3" targetFramework="net461" />
+  <package id="NUnit" version="3.9.0" targetFramework="net461" />
+  <package id="NUnit.Extension.AppVeyor.NUnit3ResultWriter" version="0.1" />
+  <package id="NUnit.Extension.NUnitV2Driver" version="3.7.0" targetFramework="net461" />
+  <package id="NUnit.Extension.NUnitV2ResultWriter" version="3.6.0" targetFramework="net461" />
+  <package id="NUnit.Runners" version="2.6.4" targetFramework="net452" />
+  <package id="NUnitTestAdapter" version="2.0.0" targetFramework="net452" />
   <package id="Rx-Core" version="2.2.5-custom" targetFramework="net461" />
   <package id="Rx-Interfaces" version="2.2.5-custom" targetFramework="net461" />
   <package id="Rx-Linq" version="2.2.5-custom" targetFramework="net461" />
@@ -20,10 +26,4 @@
   <package id="System.Security.Cryptography.Encoding" version="4.0.0" targetFramework="net461" />
   <package id="System.Security.Cryptography.Primitives" version="4.0.0" targetFramework="net461" />
   <package id="System.Security.Cryptography.X509Certificates" version="4.1.0" targetFramework="net461" />
-  <package id="NUnit.Extension.AppVeyor.NUnit3ResultWriter" version="0.1" />
-  <package id="NUnit" version="2.6.4" targetFramework="net452" />
-  <package id="NUnit.Extension.NUnitV2Driver" version="3.7.0" targetFramework="net461" />
-  <package id="NUnit.Extension.NUnitV2ResultWriter" version="3.6.0" targetFramework="net461" />
-  <package id="NUnit.Runners" version="2.6.4" targetFramework="net452" />
-  <package id="NUnitTestAdapter" version="2.0.0" targetFramework="net452" />  
 </packages>