Add parens to |> docstring

[jonniedie]

It is a common misunderstanding that
data |> x -> f(x) |> g
parses to
data |> (x -> f(x)) |> g
when it actually parses to
data |> x -> (f(x) |> g)
due to |> operator precedence. This can lead to unexpected behavior when using broadcasted pipelining. Using the docstring example with a broadcasted pipeline operator:

julia> [1:5;] .|> x->x^2 |> sum |> inv
5-element Array{Float64,1}:
 1.0 
 0.25
 0.1111111111111111
 0.0625
 0.04

julia> [1:5;] .|> (x->x^2) |> sum |> inv
0.01818181818181818

Having an anonymous function without enclosing parentheses in the docstring for |> may promote this misunderstanding.

[ViralBShah]

I feel like it is valuable to add your comment here into the function documentation. Not the broadcasted pipelining - the operator precedence.

[vtjnash]

@ViralBShah WDYT?

[ViralBShah]

@jonniedie Can you rebase to master, and we can get this merged.

[jonniedie]

@ViralBShah I... don't know if I actually did that correctly. I've never done this before.