Make gulp redundant

[neutraltone]

I propose adding DON'T USE THIS FILE to the source CSS file and make gulp return a snarky error when the user runs gulp

[Seikho]

On it

[aethant]

Go to town.

[Seikho]

See #10

[neutraltone]

Gonna need to see DON'T USER THIS FILE in the source CSS file before we can resolve this issue.

https://github.com/aethant/vanilla-css/blob/gh-pages/src/assets/css/styles.css

[Seikho]

index.html currently points to src/assets/css/styles.css (789d7e4) for its styles to circumvent the SnarkError.
assets/css/styles.css was treated as build output in #8