Handle missing compopt

Ref #5

completion.bash

@@ -40,7 +40,13 @@ _abra_complete_apps()
 
 _abra_complete()
 {
+    # https://github.com/andsens/homeshick/blob/master/completions/homeshick-completion.bash
+    if $_HOMESHICK_HAS_COMPOPT; then
         compopt +o default +o nospace
+        COMPREPLY=()
+    else
+        COMPREPLY=('')
+    fi
 
     local -r cmds='
         app
@@ -113,4 +119,11 @@ _abra_complete()
     fi
 }
 
+# https://github.com/andsens/homeshick/blob/master/completions/homeshick-completion.bash
+if type compopt &>/dev/null; then
+    _ABRA_HAS_COMPOPT=true
+else
+    _ABRA_HAS_COMPOPT=false
+fi
+
 complete -o default -F _abra_complete abra