Twenty Fifteen: edit post link text can drop a line below its icon

[celloexpressions]

Let's add white-space: nowrap; to .edit-link to avoid the edit link, which should never take up more than a line of text on any screen size anyway, from dropping a line below its icon. I don't think we can do this for any of the other post meta, as they may take up multiple lines if the author name is very long or there are a lot of categories/tags, although we may also be able to force "leave a comment" to stay on the same line with its icon (and with all three words), since that's also a known length.

[iamtakashi]

Make sure Comments Link and Edit link stay the same line with its icon.

[iamtakashi]

After:

[iandstewart]

In 30215:

Twenty Fifteen: Make sure that the edit link will always be right of it's icon.

Props iamtakashi, fixes #30171.