Adding [TestFixture] attributes.

Author: kevbite

src/HumbleConfig.Tests/KeyFormatters/KeyPostfixerTests.cs

@@ -9,6 +9,7 @@
 
 namespace HumbleConfig.Tests.KeyFormatters
 {
+    [TestFixture]
     public class KeyPostfixerTests
     {
         private KeyPostfixer _formatter;

src/HumbleConfig.Tests/KeyFormatters/KeyPrefixerTests.cs

@@ -4,6 +4,7 @@
 
 namespace HumbleConfig.Tests.KeyFormatters
 {
+    [TestFixture]
     public class KeyPrefixerTests
     {
         private KeyPrefixer _formatter;