Add method chaining style specification

[vjik]

PR is inspired by yiisoft/docs#155

Placing methods in a chain of methods on separate lines is more readable in most cases. In rare cases, this is not the case, so SHOULD.

[xepozz]

Placing ; on a separated line is handy as well.

[JesusValera]

@xepozz I don't like the single ; in a new line.
I saw some people doing it, but because they were adding new lines right after that.

$someInstance
    ->create()
    ->prepare()
    ->run()
;
$anotherInstance->run()

My suggestion is to leave a blank space:

$someInstance
    ->create()
    ->prepare()
    ->run();

$anotherInstance->run()

[xepozz]

It's just a little handy to comment/move/remove lines when you have ; not at the end of the chain, but I think it's unnecessary to have it as a recommendation :)

[andrewprofile]

in my opinion it is best to admit both versions :)

[KorvinSzanto]

I think we should change the "SHOULD" to be "MAY" and I agree that we should allow the parenthesis to be placed on the next line but maybe we can deal with that addition separately.

[samdark]

Replaced SHOULD with MAY.