Issue with short-hand values and values of 0

[bgriffith]

The shorthand-values rule doesn't work with values of zero.

Best way to replicate this is to add the following to the tests:

.value-of-zero {
  border-radius: 0;
  border-width: 0;
  margin: 0;
  padding: 0;
}

It currently returns false warnings for all of these.

Sass-lint: dev@latest

[DanPurdy]

Very odd, will look at this now