appveyor: pip fixes

Signed-off-by: Ruslan Kuprieiev <[email protected]>

.appveyor.yml

@@ -41,14 +41,11 @@ environment:
 #      PYTHON_ARCH: "64"
 
 install:
-  - cinst graphviz
   - cinst wget
   - cinst awscli
   - cinst gsutil
   - cinst openssl.light
-  - wget --no-check-certificate https://github.com/dpinney/omf/raw/master/omf/static/pygraphviz-1.3.1-cp27-none-win32.whl
-  - pip install --upgrade pip setuptools
-  - pip install pygraphviz-1.3.1-cp27-none-win32.whl
+  - pip install --user --upgrade pip
   - pip install -r requirements.txt
   - python setup.py install