polymorphic_embed is now using ParameterizedType! 
Polymorphic embeds are now specified as parameters on the field:
schema "reminders" do
field :channel, PolymorphicEmbed,
types: [
sms: MyApp.Channel.SMS,
email: MyApp.Channel.Email
]
No more intermediary module for options, code injection and macros.
Note also that for those using it, an (unrelated) bugfix requires now casting params for polymorphic embeds through cast_polymorphic_embed/2 instead of cast/4.
See example in readme.
