Add standalone build for 3.4 series

Merges the 3.3/develop branch up to 3.4/develop and updates the travis and composer configs for 3.4.x - continues kohana/kohana#50
@enov maybe I misunderstood you in [#548](https://github.com/kohana/core/pull/548#issuecomment-56636310) but did think that we'd agreed to show badges for all the current versions. FYI I've done it like this in all the modules, and they're on 3.3/develop already - so I'd have to commit and merge up reverts across the board if we want to do something else. I can do, but obviously would prefer not unless we think it's a major issue.