data-attributes (and css) removed for users with Author role

[yurig]

When using the standard WordPress editor (TinyMCE) the HTML data-attributes are removed from the HTML upon saving when the user role is Author.
data-attributes are instead preserved when the user role is Administrator.

Some css style properties are also removed from inline style attributes, like for example 'position', 'left', 'top'. Again, they are preserved for Administrators.

data-attributes and css styles are not removed when switching between Visual and Text modes in the editor, but only when publishing the post/page.

First version tested with the problem is WordPress 3.7, still existing in 3.9.

[SergeyBiryukov]

Only Administrators and Editors have the ​unfiltered_html capability by default.

[iseulde]

See above comment.