Request: foreign key support

[noinkling]

Now that Rails (>4.2) has support for database foreign keys, it would be nice to have an option for seeing these in the annotations.

[noinkling]

ActiveRecord::Base.connection.supports_foreign_keys? can be used to check if the db supports them (I think only sqlite doesn't), then ActiveRecord::Base.connection.foreign_keys("table_name") can be used to get the collection of them for any particular table.

[frank-lsf]

+1 would be really convenient!