use "my_roster" instead of "roster" in examples

It took me a while to figure out that "roster" was replaced by "my_roster" :(
Merge pull request #142 from phorque/patch-1

use "my_roster" instead of "roster" in examples
Lots of logging in test runs
We don't really need to test the default log level
Revert "[BUGFIX] Cleanup stream after each spec run"

This reverts commit 139e5ed3772c0c62b93dfab1c766ef5366e6e035.

This resulted in doubly closing streams and therefore segfaults in Nokogiri (see https://github.com/sparklemotion/nokogiri/issues/1108) and appears not to resolve the hanging issues on JRuby any more. A better JRuby solution should be sought.
Resolve some spec hanging on JRuby
Fix RSpec deprecation warnings
Add the ability to set the workqueue size

* Allow users to set the size of the GirlFriday::WorkQueue by setting
  Blather::Client.queue_size.

* The queue size is passed in as a named parameter in the last argument to
  Blather::Client.setup

* If the queue size is 0, then #receive_data will process the incoming stanza
  immediately.