A common misconception is that the indefinite pronoun "none" must always be treated as singular. The usual reason given is that "none" necessarily means "not one" (implying singularity); in fact, "none" is just as likely to imply "not any" (implying plurality). A more accurate way to assess its meaning is to recognize "none" as the negative, or opposite, of "all" and to treat it in the same way, with its number determined by the number or countability of the modifier.
Martha Kolln, in her excellent Rhetorical Grammar*, gives these examples:
Singular:
* All of the cake was left.
* None of the cake was left.
Plural:
* All of the cookies were left.
* None of the cookies were left.
The word has been used as both a singular and a plural noun from Old English onward. The plural usage appears in the King James Bible as well as the works of John Dryden and Edmund Burke, and is widespread today.
*Kolln, Martha - Rhetorical Grammar: Grammatical Choices, Rhetorical Effects, Longman Publishing Group, 5th Ed. ISBN: 9780205283057