Make Linux compatible

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

plugins/atom/atom.plugin.zsh

-local _atom_paths > /dev/null 2>&1
-_atom_paths=(
+# 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"
         "/Applications/Atom.app"
-)
+    )
 
-for _atom_path in $_atom_paths; do
+    for _atom_path in $_atom_paths; do
         if [[ -a $_atom_path ]]; then
             alias at="open -a '$_atom_path'"
             break
         fi
-done
-
-alias att='at .'
+    done
+# 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