Dbf-reader

RELEASE: BytesIO does not have a filename to print

feat: upd: now TableDefinition & FieldDefinition are only 'definitions'. Reading are in reader. So, definitions can be used by a future writer

- build: prepare version = '0.1.8'
- feat: fix: float instead decimal
- feat: upd: better formating
- feat: fix: skip deleted rows
- feat: type definition and some validations
- test: add: 100% coverage
- build: add: explicit Python 3.7 as min version
- doc: add: how to execute tests

- build: prepare version = '0.1.8'
- feat: fix: float instead decimal
- feat: upd: better formating
- feat: fix: skip deleted rows
- feat: type definition and some validations
- test: add: 100% coverage
- build: add: explicit Python 3.7 as min version
- doc: add: how to execute tests