Re-work the TShark finder
Merge pull request #20 from bbayles/reconfigure

Re-work the TShark finder
Made stoppable thread used in sniffs backwards compatible with python 2.6
Handling tshark crashes more gracefully. Note that on windows it might take too long for the tshark process to actually die so the exception may still not be raised.
Use list.append() for marginally better performance
Use str.join() for marginally better performance
Fix inaccurate docstring
XML detection fails in certain character encodings

pyshark attempts to detect XML files, but this will fail for PDML files
that don't match ANSI encoding