fixed NewFromFloat to calculate accurate values

[kotaroyamazaki]

Multiplying floats by primitive types is not precise enough, and there is a serious bug that the amount generated by NewFromFloat is different from the original value. issue : https://github.com/Rhymond/go-money/issues/121, #124

Fixed to use "github.com/shopspring/decimal" for float multiplication.

This fix requires a dependency on an external module,, but I could find no other idea.

[azlancpool]

Hello there! There is an approximate date when this change would be integrated into master? Or some other approach where this bug would be fixed?

[ahummel25]

Hello @kotaroyamazaki, is there any update on this PR? Thank you