Various changes ¯\_(ツ)_/¯

Summary of Changes:
- Betroll won't give you the greater than 90 bonus for rolling 90
anymore
- Send usage updated for clarity
- I missed some stuff when the  `config.json` stopped having "null"
everywhere, this fixes it, *I think.*
- more whitespacing in the linux guide for people like Kwoth who want to
just be able to copy paste commands

- I'm kinda just guessing this'll work so if it doesn't then, "woopsie"

src/NadekoBot/Modules/Gambling/Gambling.cs

@@ -204,7 +204,7 @@ namespace NadekoBot.Modules.Gambling
             {
                 str += "More luck next time.";
             }
-            else if (rng < 90)
+            else if (rng < 91)
             {
                 str += $"Congratulations! You won {amount * 2}{Gambling.CurrencySign} for rolling above 66";
                 await CurrencyHandler.AddCurrencyAsync(guildUser, "Betroll Gamble", amount * 2, false).ConfigureAwait(false);