Bud 0.9.5 released

[Neil Conway]

Bud 0.9.5 can be found on RubyGems. This release includes a number of
new features and bugfixes. It is also compatible with recent releases
of ruby_parser and ruby2ruby (3.0.x and 2.0.x, respectively).

Changes as follows. Note that lattice support is a pretty major
change, but it is backward compatible with previous releases. We
should do some advocacy/documentation work to explain how actually
might use lattices in practice, but I wanted to get the new release
out promptly to fix the gem compatibility issues.

* Lattice branch (Bloom^L) merged; for more info, see
http://db.cs.berkeley.edu/papers/socc12-blooml.pdf
* Compatibility with recent versions of ruby_parser (3.0.2+) and ruby2ruby
(2.0.1+). Older versions of these two gems are no longer supported
* Add support for aggregate functions that take multiple input columns
* Add built-in aggregate function accum_pair(x, y), which produces a Set of
pairs (two-element arrays [x,y])
* Support user-specified code blocks in payloads(), argagg(), argmin() and
argmax()
* Change behavior of BudChannel#payloads for channels with two
columns. Previously we returned a single *column* (scalar) value in this case;
now we always return a tuple with k-1 columns
* More consistent behavior for BudCollection#sort when used outside Bloom
programs
* Restore support for each_with_index() over Bud collections
* Restore functionality of Zookeeper-backed Bud collections and fix
incompatibility with recent (> 0.4.4) versions of the Zookeeper gem
* Optimize parsing of Bloom statements, particularly for large Bloom programs
* Fix bug in argagg state materialization
* Fix bug in chaining argmin() or argmax() expressions
* Fix bug in chaining notin() expressions

On behalf of the Bloom team:

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