Use NUnit 2.6.3 instead of 3.5.0 in AndroidResolverTests because the earlier one already exists in the project

Author: chrisyarbrough

source/AndroidResolver/unit_tests/AndroidResolverTests.csproj

@@ -37,9 +37,7 @@
 		<Reference Include="System.Core" />
 		<Reference Include="System.Data" />
 		<Reference Include="System.Xml" />
-		<Reference Include="nunit.framework, Version=3.5.0.0, Culture=neutral, PublicKeyToken=2638cd05610744eb">
-			<HintPath>..\packages\NUnit.3.5.0\lib\net45\nunit.framework.dll</HintPath>
-		</Reference>
+		<Reference Include="nunit.framework, Version=3.5.0.0, Culture=neutral, PublicKeyToken=2638cd05610744eb" />
 	</ItemGroup>
 	<ItemGroup>
 		<Compile Include="XmlDependenciesTests.cs" />

source/AndroidResolver/unit_tests/packages.config

@@ -1,4 +1,4 @@
 <?xml version="1.0" encoding="utf-8"?>
 <packages>
-  <package id="NUnit" version="3.5.0" targetFramework="net45" />
+  <package id="NUnit" version="2.6.3" targetFramework="net45" />
 </packages>