Code formatting.
Update license year.
Remove example Guardfile from doc.
DSL cleanup.

- Add attribute accessor for the options
- Use single quote string without interpolation/escape char
Add multiple CLI improvements.

- Fix broken Guard `show` and `list` actions (Fixes #389)
- Improve output for Guard `show` and `list` actions.
- Remove Bundler warning for `show`, `list` and version actions.
- Do not use the formatted logger for the Guard CLI
.