Case-insensitive attribute selectors support

[ffoodd]

Hi there,

I'm trying to use case-insensitive attribute selector (e.g. [charset="utf-8" i]) and am currently unable to compile my project. I get:

Error: unterminated attribute selector for charset when trying to compile.

Reduced test case

It's supported by sass; but at the time of writing I'm using gulp-sass. I don't think gulp-sass nor node-sass are related to the issue since as shown in the test case, compiling with libsass only doesn't work.