v1.0.0-rc1

• Breaking: Rename the Interceptor and Filter types to
  UnaryInboundMiddleware and UnaryOutboundMiddleware respectively.
• Breaking: yarpc.Config now accepts middleware using the
  InboundMiddleware and OutboundMiddleware fields.

Before:

yarpc.Config{Interceptor: myInterceptor, Filter: myFilter}

Now:

yarpc.Config{
    InboundMiddleware: yarpc.InboundMiddleware{Unary: myInterceptor},
    OutboundMiddleware: yarpc.OutboundMiddleware{Unary: myFilter},
}

• Add support for Oneway middleware via the OnewayInboundMiddleware and
  OnewayOutboundMiddleware interfaces.