Fix precision error when deserializing field to DecimalFields
Cast JSON number data to decimal.Decimal instead of float when decoding JSON
response from the SalesForce REST API.
Remove explicit cast to string for DecimalField within prep_for_deserialize

No longer necessary since any JSON number data has already been converted to
Decimal objects using parse_float=decimal.Decimal
Add Product, Pricebook and PricebookEntry models for use in tests
Add test coverage for decimal precision
Explicitly set UseStandardPrice to False to avoid INVALID_TYPE_ON_FIELD_IN_RECORD error under Django 1.6
Merge pull request #24 from jacobwegner/fix-decimal-precision

Fix precision error when deserializing field to DecimalFields