fix date comparison

[b1conrad]

this seems to work and doesn't break any pre-existing tests

[farskipper]

Good catch. Yes parseFloat is too permissive.

I think we should use _.toNumber. Here's how it works:
First it trims white space off the front and end of the string. Then it checks for hex, octal and binary number formats. Then it falls back on javascripts Number(string) type coercion which is stricter than parseFloat

"" -> 0

"2018-03-07" -> null

"1,000" -> null // should we allow commas?

"   123.45 " -> 123.45
"   123 .45 " -> null // no spaces in the numbers
"+5" -> 5
"-5" -> -5

"0xAF" -> 175    // hex
"0o72" -> 58     // octal
"0b01101" -> 13  // binary

[b1conrad]

Perfect! Many thanks, Matthew. Let's get this in soon with a minor version number bump