Fix RDKit SMILES parsing

[maclandrol]

Changelogs

• Fixes issue Decoding fragment fails on double bond, [possible bug]? #22 by making generated SAFE strings more compatible with RDKit
• Add support for labelling attachment points with branch opening label (see Decoding fragment fails on double bond, [possible bug]? #22 (comment))

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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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The original discussion related to this PR can be found here: #22.

[maclandrol]

Ping @hjuinj for review.

[hjuinj]

Thank you, Emmanuel. LGTM
May I ask will the pip package be automatically updated upon merging?

[maclandrol]

Thank you, Emmanuel. LGTM May I ask will the pip package be automatically updated upon merging?

Yes, there will be a new release after merging. I will ping you back here when it's available.

[maclandrol]

PyPi version released. conda-forge will be later in the week.

[hjuinj]

Thanks Emmanuel for the super swift resolution, and kudos on the great work on SAFE.