String calculator

• StringCalculator::add('2,3,4') returns 2 + 3+ 4 = 9
• StringCalculator::add('') returns 0
• StringCalculator::add delimiters can be , and \n
• StringCalculator::add('1,2,3,1000') returns 6 by ignoring numbers bigger than or equal to 1000

Usage

composer install
npm install
./vendor/bin/phpspec run
# or
gulp