Add parentheisis and prefer splitting on long function chaining

Often when chaining functions, e.g. long queries/maps/reduce, it's easy to get ugly code... see for example this [SO question](http://stackoverflow.com/q/34079590/1240268)!

```
a.this_is_looooooooooooooooooooooooooong_identifier.something_even_looooooooooonger_potentially.and_a_final_pretty_looooong_one
```

I think the preferred formatting is to insert parenthesis:

```
(a.this_is_looooooooooooooooooooooooooong_identifier
.something_even_looooooooooonger_potentially
.and_a_final_pretty_looooong_one
)
```

Indeed, even if you have already inserted the paren as above yapf "fixes" to:

```
(a.this_is_looooooooooooooooooooooooooong_identifier.something_even_looooooooooonger_potentially.and_a_final_pretty_looooong_one)
```

*Note: I suspect this is pretty speculative :)