Avoid duplicating images

Fixed: Multiple selectors using same image cause duplications in sprite
Thanks for @tienle and @gaugau!

Background-color bug fixed

• Fixes improper rule property in background-color extraction function.
• Fixed linter warnings in plugin tests.

Thanks for Eugene Romanovsky @setage again!)

🍺(๑˃̵ᴗ˂̵)و

Deprecation warngins fixed

Thanks for Eugene @setage

First test-proved release

0.1.0

v0.1.3

Fixed path resolving

Fixed #1, #2

Pre alpha

I will test this release on few project in production.
Use it on your own risk!