v0.27

[Ko van der Sloot]

• removed dependency on libtar
• fixed build when HAVE_TEXTCAT was not set. Improved guards agains missing textcat support

[Maarten van Gompel]

• guard against uninitialized/missing textcat (https://github.com/proycon/python-frog#22)
• require latest libfolia, ticcutils and a more recent libxml2