Quit generating implicit block after ->

[satyr]

Instead add grammar Parameters -> Expression.

Pros

We can remove the adhoc hack for jashkenas/coffeescript#1611.
f -> a.b, c will naturally work.

Cons

f -> a; b will backward-incompatibly be parsed as

f -> a
b

rather than current

f ->
  a
  b

[satyr]

On second thought, this may require additional large changes or just be too late at this point.

For example, to keep the current behavior of -> a if b (meaning -> (a if b)) -> would need to bind softer than post-if, but f -> a if b would still mean f(-> a) if b due to the way implicit call is generated.

[satyr]

→ #127