Update Readme about roxml BigDecimal deprecation (#516)
Update Readme about roxml BigDecimal deprecation (#516)

BigDecimal deprecation in ruby 2.7.0 breaks roxml dependency on this gem

https://github.com/ruckus/quickbooks-ruby/issues/515
https://github.com/Empact/roxml/issues/64
ruckus/quickbooks-ruby,ruckus/quickbooks-ruby,ruckus/quickbooks-ruby