Make Linux compatible

Just an if/else to determine if we're OSX or Linux and alias `at` appropriately.

plugins/atom/atom.plugin.zsh

@@ -1,3 +1,8 @@
+# Gets OS Type
+unamestr=$(uname -s)
+
+# If OSX
+if [[ "$unamestr" == 'Darwin' ]]; then
     local _atom_paths > /dev/null 2>&1
     _atom_paths=(
         "$HOME/Applications/Atom.app"
@@ -10,5 +15,8 @@ for _atom_path in $_atom_paths; do
             break
         fi
     done
-
-alias att='at .'
+# If Linux
+elif [[ "$unamestr" == 'Linux' ]]; then
+    # Alerts the user if 'atom' is not a found command.
+    type atom >/dev/null 2>&1 && alias at="atom" || { echo >&2 "You have enabled the atom oh-my-zsh plugin on Linux, but atom is not a recognized command. Please make sure you have it installed before using this plugin."; }
+fi