clean placeholder

[1aron]

1. line-height: 1.15 would make ::placeholder text move up ( in safari ),
   but ::placeholder { line-height: normal } could fix it.

2. make ::placeholder opacity default to 1

[Toddses]

It appears you've changed the indentation from 2 spaces to 4.

[garrettw]

Please look over #550, #587, #736 -- there has been a lot of discussion about these issues, and decisions were made on how they should be handled.

[1aron]

#776