Option to not show article on home page

Add "show_on_home_page":false to article header. The default is true for
the article to appear on the home page.
Mark articles up if only post plugins exist
Switch to using node-config
Fixed tests
Added test config file
Merge branch 'master' into config
Sort articles by date for glog tests
glog_config.json to config/default.json in strings

see #25
glog_config.json -> config/default.json in readme