title: Namespce OneTimeTearDownAttirbute () and OneTimeSetUpttirbute () does not exist in NUnit.Framework showing error in auto generated specflow(.cs) file
body: <p>Facing build error The type or namespace name "OneTimeSetUpAttribute" and "OneTimeTearDownAttribute" doesnot exist</p>
  
  <p>Xamarin.UITest-Version 3.0.0
  Nunit- Version 2.6.4
  NunitTestAdapter- Version 2.0.0 
  Specflow -Version 2.1.0.0<a href="https://i.stack.imgur.com/kbAhp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kbAhp.png" alt="enter image description here"></a></p>