I'm not longer maintaining this as there is a better, more thorough option I suggest you use. https://github.com/gorriecoe/atom-silverstripe
Based on the original https://github.com/adrexia/silverstripe-atom
I created this for me to bring it up to speed with 3.1 and to use the syntax and snippets I use most often.
To see what is available take a look through the snippets/snippets.cson file and feel free to edit and add any you prefer.