Fixed Appveyor non-recursive git clone

Author: tpeulen

.appveyor.yml

@@ -11,6 +11,8 @@ environment:
 #  - ps: iex ((new-object net.webclient).DownloadString('https://raw.githubusercontent.com/appveyor/ci/master/scripts/enable-rdp.ps1'))
 
 install:
+  - cd %APPVEYOR_BUILD_FOLDER%
+  - git submodule update --init --recursive
   - "SET PATH=%PYTHON%;%PYTHON%\\Scripts;%PATH%"
   - conda config --set always_yes yes --set changeps1 no
   - conda env create -f environment.yaml