Introduced `Datamappify.config` for configuring default behaviours
Cleaned up EOF lines [ci skip]
`map_attribute` now takes `:to` and `:provider` instead of a string for specifying data source
provider_name should be a stringe
Introduced `group` for grouping `map_attribute`, closes #8
Corrected fixture tables
Added support for entity namespaces (closes #4)
Release 0.60.0