Release v3.0.0

Version 3.0 switches the Rule Engine FLOAT data type to using Python's decimal.Decimal internally instead of float. The if, elif, else, for and while keywords are also reserved for future use now, they may not be used as symbol / variable names.

The rule_engine.ast module is also now documented as being private. Downstream projects should not reference it directly because the API may change between minor version releases in order to add new functionality.