BLD: update appveyor script to use true/false

Author: jreback

appveyor.yml

@@ -59,8 +59,9 @@ install:
   - cmd: rmdir C:\cygwin /s /q
 
   # install our build environment
-  - cmd: conda config --set show_channel_urls yes --set always_yes yes --set changeps1 no
-  - cmd: conda update -q conda
+  - cmd: conda config --set show_channel_urls true --set always_yes true --set changeps1 false
+  #- cmd: conda update -q conda
+  - cmd: conda install conda==4.0.8
   - cmd: conda config --add channels http://conda.anaconda.org/pandas
   - cmd: conda config --set ssl_verify false