Log Message:
Update shtk to 1.6:

Released on 2014-11-17.

* Added the unittest module, a framework with which to implement
  robust test programs purely in shell.  This new module supports
  defining test programs as a collection of standalone test cases or
  test fixtures; supports assert-syle vs. expect-style checks; and
  provides advanced checks to simplify the implementation of tests
  cases for command-line utilities.  unittest-based test programs
  can be trivially plugged into the Kyua testing framework.

* Added manual pages for all public API functions.  See shtk(3) for
  an introduction and follow all linked pages for details.  All
  docstrings have been removed from the code in favor of the manual
  pages.

* Added the shtk_config_include function so that configuration files
  can source other files using relative (or absolute) paths.

* Removed 'set -e' calls from shtk and from any generated scripts.
  It is the user who should be enabling this feature if he chooses to
  because 'set -e' may have suprising and inconsistent behavior in
  large scripts (and shtk can be defined as large).