Document round trip ability

[alamb]

Rationale

The property that the crate attempts to preserve "round trip ability" has come up in several PRs, most recently with @takluyver last week

Changes

1. Document the desired ability to round trip SQL in readme
2. add doc examples
3. add hints in parse_sql_statements that the verified* variants should be prefered

There are no code changes in this PR

[coveralls]

Pull Request Test Coverage Report for Build 7008526520

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• 0 of 10 (0.0%) changed or added relevant lines in 1 file are covered.
• 378 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.04%) to 87.71%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/lib.rs	0	10	0.0%

Files with Coverage Reduction	New Missed Lines	%
src/ast/query.rs	55	83.81%
src/ast/visitor.rs	56	0.0%
src/lib.rs	267	11.92%

Totals
Change from base Build 6961241850:	-0.04%
Covered Lines:	17992
Relevant Lines:	20513

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💛 - Coveralls

[alamb]

Do you have any comments about this @Dandandan / @andygrove ?

[alamb]

Thank you @andygrove

[takluyver]

Should comments be mentioned as another exception? In my brief test, comments didn't seem to be present in the AST (and I wouldn't particularly expect them) - but maybe that's planned, or there's an option I've overlooked.

[alamb]

Should comments be mentioned as another exception? In my brief test, comments didn't seem to be present in the AST (and I wouldn't particularly expect them) - but maybe that's planned, or there's an option I've overlooked.

I agree comments should be another exception