Include @import "bourbon"; for readme

[hellobrian]

Wanted to point out that scss files should include both:

@import "bourbon";
@import "neat";

Without it, I get an error:

Error compiling CSS asset
Sass::syntaxError: Undefined mixin 'box-sizing'

I could be misunderstanding the error but the solution for me was to include the @import code for bourbon and neat. 

[mehulkar]

Just had the same issue, but I got an error about an undefined variable $golden. Thanks @thisisbrianhan for filing this issue!

[wibron]

Feel free to submit a PR!

[mehulkar]

done