Parsing and printing pipe expressions with attributes

[cristianoc]

See rescript-lang/reanalyze#164

1 (@doesNotRaise [])->Belt.Array.getExn(0) formats to @doesNotRaise []->Belt.Array.getExn(0) so this is annotating the argument not the result
2 @doesNotRaise ([]->Belt.Array.getExn(0)) formats to []->Belt.Array.getExn(0) so it completely destroys the annotation.

[cristianoc]

This should be a combination of the syntax and ppx for pipe (which is in the compiler).