0.6.0

This is a major release, adding a variety of new operations and attributes
for Digraphs, as well as improving some functions and improving the
package's documentation. In this version, we welcome Luke Elliott and
Markus Pfeiffer as new authors.

New Features in Version 0.6.0

• The ability to label the edges of digraphs is introduced. [Markus Pfeiffer]
• The operation CompleteMultipartiteDigraph is introduced. [Stuart Burrell and Wilf A. Wilson]
• The operations ReadDIMACSDigraph and WriteDIMACSDigraph are introduced.
  [Wilf A. Wilson]
• The operation ChromaticNumber is introduced. [James D. Mitchell and Wilf A. Wilson]
• The operations IsDirectedTree and IsUndirectedTree are introduced. [Luke Elliott]
• The operation IsEulerianDigraphis introduced. [Luke Elliott]