title: install pygraphviz on anaconda error
body: <p>I try to install pygraphviz on Anaconda. I have done everything I found:</p>
  
  <pre><code>- install graphviz.
  - install mingw.
  - change values in the setup.py for pygraphviz as below:
     include_dirs = 'C:/Program Files (x86)/Graphviz2.38/include/graphviz'
     library_dirs = 'C:/Program Files (x86)/Graphviz2.38/lib'
  -  run python setup.py build -c mingw32 install. 
  </code></pre>
  
  <p>After step 4, I got the following error: </p>
  
  <pre><code>running install
  running build
  running build_py
  running build_ext
  building 'pygraphviz._graphviz' extension
  C:\MinGW\bin\gcc.exe -mdll -O -Wall -DGVDLL "-IC:/Program Files (x86)/Graphviz2.38/include/graphviz" -IC:\Users\garre_000\Anaconda3\
  include -IC:\Users\garre_000\Anaconda3\include -c pygraphviz/graphviz_wrap.c -o build\temp.win-amd64-3.4\Release\pygraphviz\graphviz
  _wrap.o
  pygraphviz/graphviz_wrap.c:2954:29: fatal error: graphviz/cgraph.h: No such file or directory
   #include "graphviz/cgraph.h"
                               ^
  compilation terminated.
  error: command 'C:\\MinGW\\bin\\gcc.exe' failed with exit status 1
  </code></pre>
  
  <p>Can anyone give me some advice ? </p>