Add preferredStyle to AlertOperation initializer

[felix-dumit]

I'd like to be able to use alert operation for showing an ActionSheet as well:

let alertOp = AlertOperation(presentAlertFrom: self, style: .ActionSheet)

[danthorpe]

Looks good. Happy to merge. There isn't actually a test for the style, the only thing I would add would be an assert in to check that the preferred style is set.

[danthorpe]

Hi @felix-dumit - leave a comment when you're finished / ready to merge.

[felix-dumit]

@danthorpe But it will always be set because of the default parameter?

I also want the addActionWithTitle method to return the UIAlertAction, so I can customize it or set the preferredAction property of the UIAlertController, (more practical that looping through the actions property of the UIAlertController and doing a comparison for the title.
That should be all.

[danthorpe]

Thanks for the additions! 👍😄

[danthorpe]

Yeah, it currently looks like it will always be set from the default parameter. But the test isn't just to ensure that now, it's to ensure that in the future this isn't changed or is broken.

[felix-dumit]

@danthorpe Ok I added the tests, is that what you had in mind?

[danthorpe]

Great - thanks for adding the test! Will merge shortly.