* add auto-args deserialization for RPC
* make block param member public
* change BlockParam to a more generic Trailing<T> mechanism
* define work type
* build_rpc_trait macro, implement eth protocol
* fix up tests
* move eth_filter API to new macro
* port ethcore module to new rpc macro
* port ethcore_set to auto_args
* port net RPC to auto_args
* port rpc meta api to new
* skeleton for async RPC auto_args
* macro implementations for strongly-typed async RPC wrapper
* clarify docs
* reflect new required Rust version in README
[ci skip]
