title: PyProj package installation PROJ_DIR variable
body: <p>I am attempting to install <code>pyproj</code>, although am getting a <code>Proj executable not found. Please set PROJ_DIR variable</code> error.</p>
  
  <h2>COMMAND</h2>
  
  <p><code>$ pipenv install pyproj</code></p>
  
  <p>I have also tried <code>pipenv git+https://github.com/jswhit/pyproj.git#egg=pyproj</code> for the same result.</p>
  
  <h2>OUTPUT</h2>
  
  <p><code>$ pipenv install pyproj
  Installation Succeeded
  Locking [dev-packages] dependencies
  Locking ['packages] dependancies
  Success!
  Installing dependencies from Pipfile.lock
  </code></p>
  
  <h2>ERROR</h2>
  
  <p><code>[pipenv.exceptions.InstallError]: ['Collecting pyproj==2.0.0 (from -r /var/folders/g3/912
  vtylj2hb71xf_d_8sxz480000gn/T/pipenv-qeun2uwi-requirements/pipenv-behbdii2-requirement.tx
  t (line 1))', '  Using cached https://files.pythonhosted.org/packages/53/4b/21643a93e7d33
  941498087290636e34c6d534aa8baa1ada54cf0d096ffaa/pyproj-2.0.0.tar.gz', '  Installing build
   dependencies: started', "  Installing build dependencies: finished with status 'done'",
  '  Getting requirements to build wheel: started', "  Getting requirements to build wheel:
   finished with status 'error'", '  Complete output from command /Users/darcyprice/.local/
  share/virtualenvs/pure-dawn-52933-x98m1awW/bin/python3 /Users/darcyprice/.local/share/vir
  tualenvs/pure-dawn-52933-x98m1awW/lib/python3.6/site-packages/pip/_vendor/pep517/_in_proc
  ess.py get_requires_for_build_wheel /var/folders/g3/912vtylj2hb71xf_d_8sxz480000gn/T/tmpw
  q5vvpkd:', '  Proj executable not found. Please set PROJ_DIR variable.', '  ', '  -------
  ---------------------------------']
  [pipenv.exceptions.InstallError]: ['Command "/Users/darcyprice/.local/share/virtualenvs/p
  ure-dawn-52933-x98m1awW/bin/python3 /Users/darcyprice/.local/share/virtualenvs/pure-dawn-
  52933-x98m1awW/lib/python3.6/site-packages/pip/_vendor/pep517/_in_process.py get_requires
  _for_build_wheel /var/folders/g3/912vtylj2hb71xf_d_8sxz480000gn/T/tmpwq5vvpkd" failed wit
  h error code 1 in /private/var/folders/g3/912vtylj2hb71xf_d_8sxz480000gn/T/pip-install-t_
  ap8o3w/pyproj']</code></p>