Update _vars.scss

[frannyshaw]

Change comment on line-5 from '_vars.scss' to '_defaults.scss'.

Current comment states: "Any variables you find set in inuit.css’ _vars.scss that you ...". Change to read: "Any variables you find set in inuit.css’ _defaults.scss that you ...".

Explanation follows: The core library directory inuit.css contains a file named '_defaults.scss', not the file '_vars.scss'. In fact the contents of '_vars.scss' (which we are presently reading) is intended to override '_default.scss'. This was confusing to this noobie -thanks, frannyshaw