Update changelog for 1.7.0 release.
Update changelog for 1.7.0 release.

prolixtechnikos/LiipImagineBundle,robfrawley/LiipImagineBundle,robfrawley/LiipImagineBundle,liip/LiipImagineBundle,prolixtechnikos/LiipImagineBundle,liip/LiipImagineBundle,prolixtechnikos/LiipImagineBundle