Substituted use of var name "arg" in lume.fn()

The use of a variable called "arg" was causing a bug in lume.fn() for
lua5.1 which creates a table named "arg" when a variable number of
arguments are used. The variable name has been changed to "args" to
avoid the conflict.

lume.lua

@@ -174,9 +174,9 @@ end
 
 
 function lume.fn(fn, ...)
-  local arg = {...}
+  local args = {...}
   return function(...)
-    local a = lume.merge(lume.clone(arg), {...})
+    local a = lume.merge(lume.clone(args), {...})
     return fn(unpack(a)) 
   end
 end