Bud 0.9.3 released

[Neil Conway]

Bud 0.9.3 can be found on RubyGems. This release includes a number of
significant bug fixes (including cases where programs would produce
incorrect results); it also features several notable performance
improvements. Specifically:

* Change behavior of accum() aggregate to return a Set, rather than an Array in
an unspecified order
* Fix several serious bugs in caching/invalidation of materialized operator
state (#276, #278, #279)
* Avoid possible spurious infinite loop with dbm-backed collections
* Optimize aggregation/grouping performance
* Fix bugs and improve performance for materialization of sort operator
* Fix REBL regression with push-based runtime (#274)
* Minor performance optimizations for simple projection rules
* Remove dependency on gchart
* Built-in support for code coverage with MRI 1.9 and SimpleCov

On behalf of the Bloom folks:

Peter Alvaro
Peter Bailis
Neil Conway
Joe Hellerstein
Bill Marczak
Sriram Srinivasan