NaN inputs to ActionView's NumberHelper methods will become 0.0 in order to standardize output

When writing some reporting code that ended up dividing 0.0 by 0.0 (while generating a ratio), number helpers weren't performing as expected as they didn't have any handling in place for NaN values.

I'm assuming that anytime a NaN Float value comes into a number helper, the expected return should be as if the input number was 0.0.

For example, number_to_percentage(0.0 / 0.0) should result with '0.00%', rather than 'NaN'.