Boolean flip helper for Elm

There is no such thing as !True to get a False value in Elm. 

The Elm way to achieve this is: 

```
module Helpers.Bool exposing (flip)

flip: Bool -> Bool
flip bool = 
	if bool == True then
  	False
  else
  	True

```

And the use it as:

```
import Helpers.Bool

...

Helpers.Bool.flip True
```

nickciolpan
06 May 2020