Kata

Given the string representations of two integers, return the string representation of the sum of those integers.

For example:

sumStrings('1','2') // => '3'

strsum("1", "2")    /* => 3 */

A string representation of an integer will contain no characters besides the ten numerals "0" to "9".

I have removed the use of BigInteger and BigDecimal in java

Python: your solution need to work with huge numbers (about a milion digits), converting to int will not work.