release

• BREAKING: drop support for python2/python3.5
  This is to support typing annotations (more specifically, typing module).
  If you don't have a choice of using a newer Python version for some reason, you can install the previous version (pip install 'orgparse=0.1.4'), there weren't many API changes anyway.
• better file properties handling #28 #30
• keep linenumber information in the nodes #25
• parse tables (available via body_rich property) #29
• improvements to treat OrgRootNode more like OrgNode with fallbacks