v2.9.0

• Support for IUPAC recommended primed number-letter locants e.g. 2''a
• Command-line output now includes warnings e.g. ambiguity
• SMILES writer now starts from a * atom if one is present
• Added numbering to nicotine
• Correctly interpretation of locanted perhalo terms and perhaloalkylalkanes
• Improved additive bond formation for phosphoryl
• Corrected locants on tolyl and assume p-tolyl if unspecified
• triazine is now interpreted as 1,3,5-triazine if unspecified
• Corrected interpretation of dithiazolium
• Fixed rare SMILES writing bug where slashes could be inconsistent
• Fixed ylidenethenylidene being parsed as [ylidene][thenylidene] instead of [yliden][ethenylidene]
• Fixed bug in spiro superscript inferring when a bridge is length 0