Revert "Support included blocks override"

This reverts commit 33aee12a29426987805420a410e13e0470a79cbf.

This fixes #243.
Added changelog note
Fixed warnings if Python is run with -3.

This also adds proper hashing and comparision support to
undefined objects.

This fixes #224
Corrected title filter behavior.

The title filter will now correctly lowercase the non first letter
like the regular Python filter does.

This fixes #251.
Bugfix release is today
Fixed release script
Bump version number to 2.7.1
Ready for another release
Merge branch '2.7-maintenance'