address review comments

aliases/available/uuidgen.aliases.bash

@@ -1,10 +1,10 @@
-# cite 'uuid-alias'
-# about-alias 'uuidgen aliases'
+cite 'uuid-alias'
+about-alias 'uuidgen aliases'
 
-if [ "$(uuid 2>/dev/null)" != "" ]; then # Linux
+if _command_exists uuid; then # Linux
   alias uuidu="uuid | tr '[:lower:]' '[:upper:]'"
   alias uuidl=uuid
-elif [ "$(uuidgen 2>/dev/null)" != "" ]; then # macOS/BSD
+elif _command_exists uuidgen; then # macOS/BSD
   alias uuidu="uuidgen"
   alias uuid="uuidgen | tr '[:upper:]' '[:lower:]'" # because upper case is like YELLING
   alias uuidl=uuid