Removed the complexity of a member variable which would be unnecessary for the vast majority of applications.

If users have an application with atypical requirements, they are free to override the default.

Fixed error caused by BrokenPipeError not existing in Python 2.

- poutput() can now take any argument convertible to a str via '{}'.format() instead of only str
- postparsing_postcmd() automatically runs a 'stty sane' on POSIX OSes to handle those cases of your terminal getting in a messed up state if you do something like pipe to a terminal command like "less" and then improperly quit out of it with a <Ctrl>-C instead of properly using "q"
- In _restore_output(), immeditelly restore stdout state in a finally block after closing the temporary one used for redirection/piping

Modified implementation of poutput() to accept an optional "end" argument which can change the ending to something other than a newline or simply suppress adding a newline.  Also added a try/except to catch BrokenPipeError exceptions which can occupoutputr if the subprocess output is being piped to closes before the command piping output to it is finished.

Updated install docs to note that when using Python 2.7, the subprocess32 module should also be installed.

Open them in text mode in Python 3 so self.stdout.write() expects normal Python 3 (unicode) strings.

Open them in binary mode in Python 2 so self.stdout.write() expects normal Python 2 (byte) strings.

Also fixed a unit test mocking issue on Python 2 to account for the fact that Python 2.7 requires the subprocess32 module instead of subprocess.