Dashicons: Update to the latest dashicons files.

props empireoflight, melchoyce.
fixes #26362.

git-svn-id: https://develop.svn.wordpress.org/trunk@26755 602fd350-edb4-49c9-b593-d223f7449a82
Proper CSS specificity for columns-based dashboard grids.

props kovshenin.
fixes #26354.


git-svn-id: https://develop.svn.wordpress.org/trunk@26756 602fd350-edb4-49c9-b593-d223f7449a82
Twenty Fourteen: Remove stray slash.

props Ipstenu.
fixes #26467.


git-svn-id: https://develop.svn.wordpress.org/trunk@26757 602fd350-edb4-49c9-b593-d223f7449a82