title: Can't install umbraco using nuget "operation failed"
body: <p>i'am new use umbraco cms after i try to install using nuget in visual studio 2012 i get this error</p>
  
  <p>From nuget package</p>
  
  <pre><code>'Newtonsoft.Json' already has a dependency defined for 'Microsoft.CSharp'.
  </code></pre>
  
  <p>and this from nuget console </p>
  
  <pre><code>Install-Package : 'Newtonsoft.Json' already has a dependency defined for 'Microsoft.CSharp'.
  At line:1 char:1
  + Install-Package UmbracoCms
  + ~~~~~~~~~~~~~~~~~~~~~~~~~~
      + CategoryInfo          : NotSpecified: (:) [Install-Package], InvalidOperationException
      + FullyQualifiedErrorId : NuGetCmdletUnhandledException,NuGet.PowerShell.Commands.InstallPackageCommand
  </code></pre>
  
  <p>how to solve this</p>