Removed escape character from replacment string in string.gsub calls

This should fix errors with Lua 5.2 ("Lua runtime error: viddy.lua:267: invalid use of '%' in replacement string.", etc) Apparently Lua 5.1 was more lenient with escape characters than 5.2 (http://lua-users.org/lists/lua-l/2010-02/msg00708.html).