title: Initialze a tuple of tuples
body: <p>I can initialize a <code>std::tuple</code> like this</p>
  
  <pre><code>std::tuple&lt;int,float&gt; t1{ 1,2.2 }; // works
  </code></pre>
  
  <p>If I want to initialize a tuple of tuples:</p>
  
  <pre><code>std::tuple&lt;std::tuple&lt;int,float&gt; &gt; t2{ 1,2.2}; // fails on gcc5.2.0 &amp; gcc6.1.0
  std::tuple&lt;std::tuple&lt;int,float&gt; &gt; t2{{ 1,2.2}}; // works on gcc6.1.0, fails for gcc5.2.0
  </code></pre>
  
  <p>So I am a bit confused if one of the above lines is correct c++14 code or not.</p>
  
  <p>Simple question: Is it possible to direct initialize a tuple of tuples without using <code>std::make_tuple</code> or other helper types?</p>
  
  <p>I am a bit in fear because of other problems found today like: <a href="https://stackoverflow.com/questions/37186443/confusion-while-deriving-from-stdtuple-can-not-handle-stdget/37188019#37188019">Confusion while deriving from std::tuple, can not handle std::get</a></p>