Dagger 1.x and 2.x are incompatible. Rather than choose one over the
other, this change removes Dagger completely. Users can now choose any
injector, constructing Feign via its Builder.
This change also drops support for javax.inject.Named, which has
been replaced by feign.Param.
see #120
The logic in GsonCodec was split into GsonEncoder and GsonDecoder, each of which can
now be used separately. GsonCodec was deprecated, and can be removed in the next major
version. To facilitate use outside of Dagger, the double-to-int map type adapter was broken into
its own class, and is included by default when using the default constructors of either the
encoder or decoder. The examples have been updated to use the new encoder/decoder instead
of the codec.