More flexible handling of infix operators

I'd like to throw out there that instead of special casing `<|` we just give more flexibility to infix operators, and not manipulate them by default. Instead if a operator is found on a new line, elm-format could line it up with other operators found on new lines, but leave them alone otherwise. Right now I find myself frequently adding parenthesis to stop elm-format from making my code less readable.

If I wrote the following, I'd prefer elm-format not alter it in any way:

``` elm
foo x =
fn ++ bar
<| a 1
<| b 2 ++ baz
<| c 3
```

I don't find the above code to be unreasonable, or unreadable.

The issue names no files, tests, or entry points. Begin by locating elm-format’s handling of infix operators and comparing it with the provided Elm example. Done requires an agreed rule for preserving or aligning operators and tests that demonstrate the intended formatting behavior.

Written by the indexing model from the issue text.