give fully usable Cargo.toml on hc generate zomes/x rust

[Connoropolous]

This is usable:

[package]
  name = "code"
  version = "0.1.0"
  authors = ["Author Name <authoremail@gmail.com>"]
  edition = "2018"
[dependencies]
  serde = "1.0"
  serde_json = "1.0"
  hdk = { git = "https://github.com/holochain/hdk-rust" }
  serde_derive = "1.0"
  holochain_wasm_utils = { git = "https://github.com/holochain/holochain-rust" , branch = "develop" }
[lib]
  path = "src/lib.rs"
  crate-type = ["cdylib"]