Add auto-complete and improve history support

Overview

• Add auto-complete support
• History is now sorted by time and includes how long since last use
• --cache option is no longer supported
• Lots of code cleanup & quality improvements

What's Changed

• add and improve code report card by @synfinatic in #125
• Fix more golint errors by @synfinatic in #126
• add codecov support by @synfinatic in #127
• fix readme by @synfinatic in #128
• Add auto-complete support by @synfinatic in #129
• Add timestamp to history & fix sorting by @synfinatic in #130

Full Changelog: v1.2.3...v1.3.0