Remove star property hack

[frozenbonito]

tachyons-sass/scss/_clears.scss

Line 21 in 2dce89b

.cf { *zoom: 1; }

The star property hack is not valid CSS, so it breaks modern css parses.
I think it is safe to remove it because only very old browsers (IE 5.5 to 7) support it.

related:

• Remove IE6/7 prefix support tachyons#699
• Remove IE7 CSS hack swagger-api/swagger-ui#7526

[silverwind]

#63