Emitter fixes

- Limit the total size of buffered events, and drop events if we have too many.
- Split up large eventLists into batches.
- Add http emitter configs maxBatchSize, maxBufferSize.
- Update to http-client 0.9.7, java 1.7.
- Fix various tests.
no, for a couple reasons:

- the HttpPostEmitter doesn't know what an alert is and can't make them.
- if it's having problems emitting alerts, it can't alert anyway.