Add focus argument in Terminal.prototype.open

[parisk]

Fix #640

[coveralls]

Coverage decreased (-0.1%) to 68.708% when pulling 35f746c on issue-#640-do-not-focus-on-open into 944da28 on master.

[parisk]

Opened up a documentation PR as well: xtermjs/xtermjs.org#20.

[Tyriar]

I don't think we should add an option to the API, isn't this the same as doing this?

term.open(el);
term.focus();

We could call it out in the release notes as a minor change, I don't see it breaking many applications though.

[parisk]

@Tyriar, this will break all applications that use xterm.js actually, since the focus will be elsewhere now.

Since this is changing the way it works and it is a user facing issue, I don't want to break the API in a minor release. It's a very simple piece of code, which can go away in the next major release.

[Tyriar]

Sounds good 😄

[coderaiser]

Would be better to use options object instead of last boolean argument in v3. This way:

term.open(container, {
    focus: true
});

It is much cleaner and obvious then last boolean parameter.
What if there should be some other options, not only focus in a future?

[Tyriar]

A new object might cause confusion with Terminal(options). I would prefer if we removed the parameter outright in v3 so it's ignored.

[parisk]

I agree. Keeping this in options sounds quite better.