update script/server for jekyll 3

.gitignore

@@ -11,3 +11,4 @@ assets/vendor/qtip2/basic
 .ruby-version
 /tmp
 Gemfile.lock
+.jekyll-metadata

script/server

@@ -3,7 +3,7 @@
 set -e
 
 echo "spinning up the server..."
-bundle exec jekyll serve -w
+bundle exec jekyll serve --watch --incremental --trace
 
 echo "cleaning up..."
 rm -Rf _site