use lua function names instead of blizzard's special names

diff --git a/WeightsWatcher.lua b/WeightsWatcher.lua
index b0ae418..fbce155 100644
--- a/WeightsWatcher.lua
+++ b/WeightsWatcher.lua
@@ -845,7 +845,7 @@ end
 function WeightsWatcher:preprocess(text)
 	for pattern, replacement in pairs(Preprocess) do
 		if string.find(text, pattern) then
-			text = gsub(text, pattern, replacement)
+			text = string.gsub(text, pattern, replacement)
 		end
 	end