Remove need to specify overrides = true

[codefromthecrypt]

When Module(overrides=true) is set, any @Provides(type = SET) methods will override as opposed to adding to ones specified by feign.

This leads to hacks inside ReflectiveFeign like below, which manually enforce a base set of decoders. These cannot be overridden by dagger at all.

      this.decoders.put(void.class, stringDecoder);
      this.decoders.put(Response.class, stringDecoder);
      this.decoders.put(String.class, stringDecoder);

As soon as Dagger 1.1 is out (likely this week), we'll have access to the SET_VALUES feature, which should allow us to eliminate the troublesome Module(overrides=true) features.

With this in, we should update examples and any how-to docs to show how to wire up feign so as to not require or suggest Module(overrides=true), except in very specific cases.

cc @benjchristensen

[codefromthecrypt]

dropped support for dagger in #141