Fix AppVeyor - end2end tests need installed gl binary

Author: techtonik

.appveyor.yml

@@ -33,6 +33,7 @@ before_test:
 
 test_script:
   - ps: |
+      &$env:PYTHON -m pip install .
       &$env:PYTHON setup.py nosetests --logging-level=WARN --with-xunit 
       if ($LastExitCode -ne 0) { $host.SetShouldExit($LastExitCode) }
       # upload results to AppVeyor