fix (main,book_bars,helpers): fix cargo warnings

[mattgathu]

Fixed unused import warnings:

• unused import: std::mem
• unused #[macro_use] import
• unused import: Emoji

[crowdagger]

Thanks for the contribution! However, I probably won't be able to merge this PR as I am currently refactoring things quite a bit and code has already evolved locally so it's a bit of a mess. Sorry, probably should have created another branch for that :)

[mattgathu]

Alright. Hoping to see the updated code on github soon. I was also working on several other PRs, I guess I will have to ditch them and wait.

[crowdagger]

Code should now be a bit more stable. Sorry about the inconvenience, I'm used to be a bit alone on the repo :)