Binary: add expected trigger.

- Add expected trigger "decimal 3 to binary" which fixes #291
- Add complementary trigger for 'hex' where it may be ambiguous.
- Normalize hex conversion output.
- Add additional prepositions which imply conversion ('as', 'into')
- Adjust output style to be more like other IAs.
- Improve comments, albeit very slightly.
- Add additional tests, including covering all example queries.
- Add ABSTRACT to reduce scroll spam under `dzil test`