Improve exception handling

Ignore exceptions while flushing and make sure a new timer is always
set.

With the old code if there was any exception while flushing, e.g. an
error while connecting to Graphite, the process would not flush anymore.
refactor the main "process" function for pystatsd

* Eliminate bogus metrics right up front.  Warn and drop them.
* Rename variables: data, fields, bits, bit... lots of overly
  generic names.  Instead, produce four clear variables: key, value,
  mtype, and rest.
* Break the big if/else's clauses into distinct functions to be
  easier to read on their own.
* Avoid some type mismatches.  Previously, an Int could end up in
  what would otherwise be a List of Str.
Merge pull request #61 from pneff/exceptions

Improve exception handling
Merge pull request #72 from rjbs/master

refactor server process(), clarifying code and fixing bugs
add incr and decr aliases to client (because typing those extra 5 characters, my God.) Add debug-friendly repr() for client.
version bump