Fix bug in error logging during persistence.
Merge pull request #72 from jrmehle/fix_error_logging

Fix bug in error logging during persistence.
Cast values based on their declared Salesforce FieldTypes when building SObjects from a response.
Merge pull request #73 from llhupp/better_typecasting

Better typecasting when building SObjects
Fix `SObject#update!` not specifying `Id` to the Restforce client for persisted records.
Merge pull request #74 from llhupp/fix_update

Fix `SObject#update!` not specifying `Id` to the Restforce client for persisted records.