Autodesk's DXF format reference
simplest dxf file with a line in it
moved handle generation into the builder
Added lightweight polyline entities
Added layers and line types
Added current layer variable
Added 'curvy' entities: point, circle, arc, ellipse
Version bump to 0.0.0
get ready for very first 'release'
Version bump to 0.0.2
better check for IO-like object (respond_to? :printf)