RPC API

[liamcurry]

All EOS apps need a way to talk to EOS nodes, to fetch table rows and to send transactions. In order for full-stack Rust-based EOS applications to come to fruition, there needs to be a solid RPC API. In Javascript there is eosjs, and something similar should exist for Rust.

Implementing this will be a little tricky since we need to support browsers and server environments. In the browser we will need to support wasm-bindgen and stdweb, and on the server we should support hyper. This could get even more complicated if we decide to optionally support futures. This may be a 1.0+ feature.