add clojars repository so maven can find riemann-java-client
Feature parity with reporter that comes with riemann java client

- Brings back tags, prefixes, configurable separators, and ability to
  set source host name.
- Change defaults to match the Riemann yammer metric reporter (ttl is
  nil, etc).
- Add some more error handling to prevent crashes caused by odd edge
  cases.
- More.
Use the riemann batch client class

Use the included batch client class instead of rolling our own. The
previous batching implementation sent all metrics gathered at once,
while the batch client class has a configurable batch size. This will
help in avoiding overloading the riemann server by sending it too many
metrics at once.
Remove all custom batching support from reporter

Remove all custom batching support from reporter as batching will now be
provided by the batching client.

Also refactor to eliminate as much redundant code as possible.