Issues Fixed

#15 - Config option (stalled_job_buffer) to save off # most recent lines of output (per host). Initial Ctrl-C interrupt will output to console the recent output from the potentially stalled nodes, which may originally have occurred hundreds or thousands of lines above the current console position.
#16 - Misuse of catching AttributeError when calling plugin lookup() function. Now use hasattr() call to pre-screen, and if plugin lookup() call raises AttributeError, it gets logged as with any other exception.
#17 & #11 - Better detection of remote host "going away". Paramiko keepalive doesn't check for responses, so request packets just wind up getting queued. Implement a keepalive system that can detect lack of responses.

Enhancements

Better internal handling of byte data versus character data (Unicode). Initial Python3 port effort wound up breaking all handling of output that was not 7-bit clean ASCII. While there may still be gremlins lurking, this should make things a whole lot better for both Python2 and Python3. Override default of sys.stdout.encoding with config option character_encoding.
Include per-host connection status in radssh.log file.

New plugin: alias
Permits local shell aliases to be used within remote clusters. Alias definitions may be sourced from ~/.bash_profile, ~/.bashrc or ~/.profile (sh), on a first-found basis. Also permits !! and !$ to be interpreted.
New plugin: tar
Allows quick collection of logfile or config file directories, using *tar (or *tgz / *tbz) to invoke tar (and compress) on remote nodes with subsequent command line args as the files or directories to gather.
*tty Would report that it was skipping hosts, without actually skipping them.