Linter script performance enhancement

[heyheyjp]

The linter script takes too long to complete. The 400+ warnings printed are probably related. Let's fix those warnings or update the code or .eslintrc to ignore.

[lumodon]

PR: #1101
Blocked due to codeclimate failure - "Similar code found in 1 other location"
https://codeclimate.com/github/LearnersGuild/echo/pull/1101