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
Well, 3.2 is "not-even-supported-by-the-community-team-unsupported" (and it doesn't have Travis builds) - so I don't see an issue with leaving it out. There's still a 3.1/master and 3.0/master too...

When (if) we ever get a 3.5 or 4.0, then presumably that will be the point that we stop supporting 3.3 (unless you think the community team is likely to have time and inclination to support 3 versions?!). At that point 3.4/master becomes the default branch and the 3.4 readme gets updated to show 3.4 and 3.5.