Changed the --out-format optional argument passed to rsync.
Added comment TODO list for implementing the trigger feature.
Added unit test, comments and bug fix for rsyncWrapper.wait method.
Make PipeLogger build a biggest files list and bytes transferred tally.
Add keyword arguments bw_warn and bw_err to PipeLogger constructor.
Make PipeLogger().run() check bw_err and bw_warn.

At any point, if bytes_count exceeds bw_err, abort the backup.
If and when the backup completes, and bytes_count exceeds bw_warn,
log a warning message.
Added the bw_warn and bw_err configuration keys.
Made Cycle interruptible by PipeLogger thread through an event object.

While Cycle instances wait for the rsync subprocess to finish, it also
monitors the kill_switch_event that might be set by a PipeLogger
instance, and also handles KeyboardInterrupt. In both cases, it kills
the rsync subprocess.

The interrupt_event instance attribute of the PipeLogger class is
removed. Logging must continue until the end of the stream. There is no
need to talk to the thread if the subprocess is killed and it stops
outputting to stderr and stdout.
Added the FLAGGED status in the snapshot module.
Added the --force command line option.
Improved README.rst, added backup.1.rst man page, bump to version 1.