Major cleanup.

- Use `irc.foo` notation instead of `irc:foo`. It still
  supports the `irc:foo` usage, but will helpfully issue
  a warning with the location of the offending code.
- Remove unused arguments from functions.

.luacheckrc

@@ -1,5 +1,4 @@
 
-unused_args = false
 allow_defined_top = true
 
 read_globals = {
@@ -11,4 +10,5 @@ exclude_files = {
 }
 
 globals = {
+	"irc",
 }