v0.2.0

Fixed

• Kekulization of imidazole cycle of L-histidine residues.

Changed

• Refactored API to make failible operations return a result.
• Renamed AminoAcid::from_code1 to AminoAcid::from_char.
• Renamed AminoAcid::from_code3 to AminoAcid::from_code.

Added

• AminoAcid::as_code to view the 3-letter code of an AminoAcid variant.
• L-pyrrolysine, dehydroalanine and (Z)-dehydrobutyrine amino acids.
• Support for cross-link modifications like cystine or lanthionine.
• Support for head-to-tail homodetic cyclization.
• Dedicated error type for the new possible errors.