chore(ci): need to install gh-pages

Author: richardschneider

appveyor.yml

@@ -25,6 +25,8 @@ environment:
 # tools we need for bulding/testing/deploying
 install:
   - choco install gitversion.portable -pre -y
+  - npm install gh-pages -g
+
 #  - nuget install secure-file -ExcludeVersion
 #  - if defined snk_secret secure-file\tools\secure-file -decrypt src\ipfs.ci.snk.enc -secret %snk_secret% -out src\ipfs.dev.snk
   - choco install ipfs