Reengineer rendering fixer callbacks

- Overriden render_*() methods did not use fixer callbacks.
- No longer necessary to override render_*() methods.
- Provide default (common) callbacks by supported_fixers itself.
Improve message rendering for 외환카드
Add support for 삼성카드 (#20)
Modify description for 삼성카드
Merge pull request #21 from tomyun/samsungcard

삼성카드 지원 추가