lib/log: shellcheck && shfmt

Alsö, fix tests to load `lib/colors` instead of `lib/appearance`...wut

Alsö, `short-circuit _has_colors()`: If we already looked up colors, and we already have them, then don't run `tput` again.

My apologies to future `git blame` hunters ♥

clean_files.txt

@@ -78,6 +78,7 @@ completion/available/vuejs.completion.bash
 completion/available/wpscan.completion.bash
 
 # libraries
+lib/log.bash
 lib/utilities.bash
 
 # plugins