split packets on any line ending using built-in method

Certain conditions around sending packets with CRLF line endings may
cause a KeyError exception to be raised. This changes the split() method
to not be specific to '\n', rather use the python splitlines() builtin
method to ensure we do not neglect Windows systems.

Fixes #1023 
Also includes some Rakefile task reorganization and addition of a `rake clean` task.