math class update [0.9.0]

This version introduces multiple enhancements:

added new method to calculate difference between two numbers in percent

Details of additions/deletions below:
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Modified:   /Lib/Core/Blue/Helper/Math.php
            -- Added --
                calculate difference in percent

Modified:   /Lib/Core/Blue/etc/config.ini
            -- Modified --
                changed version from 0.8.1 to 0.9.0