Update edition

[parasyte]

Updates much of the syntax to Rust 2018 edition.

• Remove extern crate
• Use new module naming convention
  • E.g. src/tui.rs instead of src/tui/mod.rs
• Use pub(crate) visibility modifier where possible
  • Not able to use this in the search module because lalrpop generated code doesn't support it.
  • See: Generated source contains pub lalrpop/lalrpop#519
• Use crate:: or self:: path specifiers to reference modules within the crate.
  • This solves the ambiguity between the tui crate and the tui module, for example
• Rename redundantly named submodules like tui::tui to tui::types
• Directly use macros by full path
• Update lalrpop to newest stable release
• cargo fmt updated some minor syntax things, like removing redundant commas on some match arms.

[psurply]

This change looks good to me. Thanks a lot!