RPC & Client (#21)

* Initial version of http server.

* Refactor the structure.

* add unassigned ports info.

* Rename servers to match conventions.

* Add client crate and some proper RPC implementations.

* Style & docs.

substrate/contracts/src/lib.rs

@@ -42,6 +42,6 @@ pub mod error;
 pub mod executor;
 
 /// Creates new RustExecutor for contracts.
-pub fn new() -> executor::RustExecutor {
+pub fn executor() -> executor::RustExecutor {
 	executor::RustExecutor::default()
 }