Set PHP 5.4 as requirement

If we set PHP 5.4 as requirement, we could make usage of traits.

I think PHP 5.4 is very common on the most web hosters now. It was already released on 1st March 2012.

[adamlundrigan]

This is always a question of balance. IMO you are right that the vast majority of people are no longer using <= 5.4, but is it worth excluding those who do just to save ~30 lines of boilerplate code? That said, 5.3.x is EOL this month so those still using it should have no reasonable expectation that new code will be fully compatible with it. I'm leaning towards agreeing with you and bumping the minimum version to 5.4.0...