Fix the "-w" option

Fixed a reference to a non-existent variable which was causing the "-w"
option to have no effect.
Fix a couple of error messages

Fixed an error message that was trying to output the wrong information (it
was causing btest to terminate with a python stack trace).  Improved
a different error message by including the test filename that was
triggering the error.

Also fixed a typo in the help output.
Fix typos and reST formatting in README
Merge remote-tracking branch 'origin/topic/dnthayer/bug-fixes'

BIT-1070 #merged

* origin/topic/dnthayer/bug-fixes:
  Fix typos and reST formatting in README
  Fix a couple of error messages
  Fix the "-w" option