0.2.3
  * version.rb script - versioned install
  * support for $transaction, modifications to transaction, begin_transaction,
    end_transaction
  * added DEFAULT_VT_BEGIN, default_vt_begin, etc.
  * support to use ri_violators with *btpk
  * ensure block added to can_cascade
  * added method btpkgen
  * added method select_timeline
  * fix to set_btpk where a btpk of '' was considered valid...
0.2.0
  * clean up lib/*.rb under 'ruby -w'
  * clean up lib/*.rb for ruby 1.8.0
  * changed return value of BtPgsql::Relation#rows_referencing from 
    [[[]],[[]]] to [[],[]]
  * added constraint to btfkactions in sql/btschema.sql
  * adjusted impl of @can_cascade in seq_delete and seq_update, behaviour is
    identical though
  * seq_delete now handles 'no action' and 'restrict' (raises error)
  * seq_update didn't ever NEED to check foreign keys in order to determine an
    update_action since ONLY non-private (!@pk and !@btfield) fields can be
    modifieds and ONLY @pk fields can be referenced by a foreign key  - in
    otherwords nothing which can be updated can be pointed at by a foreign key
  * made install go into destdir/btpgsql with btpgsql.rb simple doing
    appropriate require
  * streamlined BEGIN/END blocks (setup/teardown) for test/btpgsql.rb
0.1.0
  * allow seq_insert to insert with future tt_start
  * small bug fixes
  * added some tests
0.0.0
  * initial release