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String Calculator Tasks
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- Create a simple String calculator with a method int Add(string numbers)
    - The method can take 0, 1 or 2 numbers, and will return their sum (for an empty string it will return 0) for example `""` 
    - or `"1"` or `"1,2"`
    - Start with the simplest test case of an empty string and move to 1 and two numbers
    - Remember to solve things as simply as possible so that you force yourself to write tests you did not think about
    - Remember to refactor after each passing test
- Allow the Add method to handle an unknown amount of numbers
- Allow the Add method to handle new lines between numbers (instead of commas).
    - the following input is ok:  `1\n2,3`  (will equal 6)
    - the following input is NOT ok:  `1,\n` (not need to prove it - just clarifying)
    - Support different delimiters
    - to change a delimiter, the beginning of the string will contain a separate line that looks like this:   `//[delimiter]\n[numbers…]` for example `//;\n1;2` should return three where the default delimiter is ‘;’ .
    - the first line is optional. all existing scenarios should still be supported
- Calling Add with a negative number will throw an exception `negatives not allowed` - and the negative that was passed.if there are multiple negatives, show all of them in the exception message

> stop here if you are a beginner. Continue if you can finish the steps so far in less than 30 minutes.

- Numbers bigger than 1000 should be ignored, so adding 2 + 1001  = 2
- Delimiters can be of any length with the following format:  `//[delimiter]\n` for example: `//[***]\n1***2***3` should return 6
- Allow multiple delimiters like this:  `//[delim1][delim2]\n` for example `//[*][%]\n1*2%3` should return 6.
- make sure you can also handle multiple delimiters with length longer than one char

Add original requirements from osherove's site
Add original requirements from osherove's site
