v0.3.0

Backboner v0.3.0

Diff since v0.2.0

• Added documentation (incomplete).
• Added Residue type with fields: index, backbone (the entire backbone of the parent chain), aa (amino acid), and ss (secondary structure).
• Added the backbone_atom_coords function to get the coordinates of the backbone atoms of a residue, represented by a 3x4 matrix.
• Added aavector field to Chain.
• Chain is now a subtype of AbstractVector{Residue}.
• The add_oxygens function no longer removes the last residue of a Backbone{3} when creating the Backbone{4}. Instead, it selects a random orientation for the oxygen atom of the last residue.
• Secondary structure of chains are now represented by Chars according to the standard for DSSP classification.
• Removed SecondaryStructure type.