Upgrade wagtail-modeltranslation for wagtail 1.4.x.
Upgrade wagtail-modeltranslation for wagtail 1.4.x.

The `release/v0.5` branch of wagtail-modeltranslation supports changes
made in wagtail 1.4.x.

okfn/rtei,okfn/rtei,okfn/rtei,okfn/rtei