Fix bug in canonical due to for loop on set

[maclandrol]

Changelogs

• fixes output is not deterministic (?) #15 caused by iteration on set even for canonical encodings
• various typos in docs fixed

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Checklist:

• Add tests to cover the fixed bug(s) or the new introduced feature(s) (if appropriate).
• Update the API documentation if a new function is added, or an existing one is deleted. Eventually consider making a new tutorial for new features.
• Write concise and explanatory changelogs below.
• If possible, assign one of the following labels to the PR: feature, fix or test (or ask a maintainer to do it for you).

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This PR fixes the #15 for canonical SAFE strings, which was caused by failure to account for order in sets.

[kjappelbaum]

can confirm that this fixes the issue! Thanks for the fast turnaround!