Changed lume.fn/once's returned func return, v1.0.8

* The functions which lume.fn() and lume.once() return now return their
  inner functions' return value instead of nil
* Moved lume.once() in lume.lua and README.md to be near its similar
  functions -- lume.fn() and lume.time()

README.md

@@ -121,15 +121,6 @@ exist in the table.
 lume.find({"a", "b", "c"}, "b") -- Returns 2
 ```
 
-### lume.once(fn, ...)
-Returns a wrapper function to `fn` which takes the supplied arguments. The
-wrapper function will call `fn` on the first call and do nothing on any
-subsequent calls.
-```lua
-local f = lume.once(print, "Hello")
-f() -- Prints "Hello"
-f() -- Does nothing
-```
 
 ### lume.slice(t [, i [, j]])
 Mimics the behaviour of Lua's `string.sub`, but operates on an array rather
@@ -149,6 +140,16 @@ local f = lume.fn(print, "Hello")
 f() -- Prints "Hello"
 ```
 
+### lume.once(fn, ...)
+Returns a wrapper function to `fn` which takes the supplied arguments. The
+wrapper function will call `fn` on the first call and do nothing on any
+subsequent calls.
+```lua
+local f = lume.once(print, "Hello")
+f() -- Prints "Hello"
+f() -- Does nothing
+```
+
 ### lume.time(fn, ...)
 Inserts the arguments into function `fn` and calls it. Returns the time in
 seconds the function `fn` took to execute followed by `fn`'s returned values.