strip trailing newlines on incoming data

some clients send a newline at the end of each metric, using it
as a terminator rather than a delimiter; cope with it
handle multimetric transmissions

a transmission consists of one or more metrics separated by
newlines; see https://github.com/b/statsd_spec

With this patch, pystatsd should handle incoming transmissions
that provide more than one metric at once.
look for counters as such, warn on unknown types
correct a log message
delete, do not clear, flushed timers

They are already reinitialized as needed, and deleting them leaves
the system primed for an IndexError:

  File ".../py-statsd/pystatsd/server.py", line 111, in process
      self.timers[key][0].append(float(fields[0] or 0))

...because there will be no [0] in the timer.  Fortunately, timer
lists are initialized as needed, so deleting this seems to make
everything do the right thing.
Merge pull request #69 from rjbs/multimetric-process

fix timer handling, handle multimetric transmissions