Added 5.3.1 to travis builds, as this is the oldest supported version.
Merge branch '1.6' into 1.7
Merge branch '1.7' into 1.8
Looks like PHP 5.3.1 doesn't exist on travis. 5.3.3 should though.
Merge branch '1.6' into 1.7
Merge branch '1.7' into 1.8
Added PHP 5.5 to travis testing list.
Merge branch '1.5' into 1.6
Merge branch '1.6' into 1.7
Merge branch '1.7' into 1.8
Merge branch '1.8'

Conflicts:
	.travis.yml