Clarify placement of function keyword

[Smaug123]

Fixes #27. Also an unrelated drive-by correction of a misaligned function keyword.

[rdipardo]

A suggestion for a small addendum: demonstrate a pattern match using a direct pipe into function, like this example:

[ 'a'; 'b'; 'c' ]
|> List.tryFind (fun c -> c = 'c')
|> function
| Some c -> c
| None -> 'd'

I've probably missed something, but I haven't been able to find explicit guidance on whether option branches following |> function should be indented or aligned with the keyword as in a match _ with construct.

Consider this illustration of piping into match:

let bar =
    baz
    |> (
        match false with
        | true -> id
        | false -> id
    )

If baz were applied to function instead, one might expect the branches to be indented no farther than the keyword, as above. However, it matters to fantomas whether the expression is parenthesized:

Code

let bar =
    baz
    |> (
        function
        | true -> id
        | false -> id
    )

Result

let bar =
    baz
    |> (function
    | true -> id
    | false -> id)

Remove the parentheses, and the matches receive extra indentation as in a multiline lambda (on which the published guide already gives advice regarding indentation):

let bar =
    baz
    |> function
        | true -> id
        | false -> id

I may just be sounding off here (indeed, I've been told so already), but my intuition is that the accepted style of match _ with (no indent) might as well apply to |> function when they're syntactically and functionally equivalent.