Investigate runner

[epage]

See https://github.com/stevedonovan/runner/

[epage]

• Wraps in a main with Result<(),Box<Error+Sync+Send>> return type
• Has standard prelude
  • First-run writes out the prelude and then users can edit it
• No per-script dependency specifications but instead a global list of dependencies (like the playground)
• //: allows specifying runner arguments inside the script itself
• Has a lot of flags to interact with the shared Cargo.toml
• -e <expr> support
• -i <expr> for special iterator support
• -n <expr> for per-input-line expressions