title: cvxpy stlibc++ Installation error on MacOS Mojave
body: <p>While trying to install cvxpy package using pip install on Mac, I get the following error message:</p>
  
  <pre><code>warning: include path for stdlibc++ headers not found; pass '-std=libc++' on the command line to use the libc++ standard library instead [-Wstdlibcxx-not-found]
  In file included from cvxpy/cvxcore/src/cvxcore.cpp:15:
  cvxpy/cvxcore/src/cvxcore.hpp:18:10: fatal error: 'vector' file not found
  #include &lt;vector&gt;
  ^~~~~~~~
  1 warning and 1 error generated.
  error: command '/usr/bin/clang' failed with exit status 1
  </code></pre>
  
  <p>Mac is running OS Mojave.</p>