Number in range validator

Hello,

I created a range validator. I think it may be usefull to include it in the library.

Please note that I **changed the number validator's regexp**, so it accepts negative values, forces to have at least one decimal number (refuses ".") and refuses if there's no value after a decimal point (such as "0.").
Downside is: it will refuse the scientific input ".5" (but will accept "0.5").
I based my regexp from the one in the [MDN's parseFloat documentation](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/parseFloat#A_stricter_parse_function).
Tests have been updated accordingly.

Please let me know if you need anything else.
Have a nice day!