CHANGES IN VERSION 1.8
-----------------------

NEW FEATURES

    o Added asBED and asGFF methods to convert a TranscriptDb to a
      GRanges that describes transcript structures according to either
      the BED or GFF format. This enables passing a TranscriptDb
      object to rtracklayer::export directly, when targeting GFF/BED.

CHANGES IN VERSION 1.6
-----------------------

NEW FEATURES

    o TranscriptDbs are now available as standard packages.  Functions
    that were made available before the last release allow users to
    create these packages.

    o TranscriptDb objects now can be used with select

    o select method for TranscriptDb objects to extract data.frames of
    available annotations.  Users can specify keys, along with the
    keytype, and the columns of data that they want extracted from the
    annotation package.

    o keys now will operate on TranscriptDB objects to expose ID types
    as potential keys

    o keytypes will show which kinds of IDs can be used as a key by select

    o cols will display the kinds of data that can be extracted by select

    o isActiveSeq has been added to allow entire chromosomes to be
    toggled active/inactive by the user.  By default, everything is
    exposed, but if you wish you can now easily hide everything that
    you don't want to see.  Subsequence to this, all your accessors
    will behave as if only the "active" things are present in the
    database.

SIGNIFICANT USER-VISIBLE CHANGES

    o saveDb and loadDb are here and will be replacing saveFeatures
    and loadFeatures.  The reason for the name change is that they
    dispatch on (and should work with a wider range of object types
    than just trancriptDb objects (and their associated databases).

BUG FIXES

    o ORDER BY clause has been added to SQL statements to enforce more
    consistent ordering of returned rows.

    o bug fixes to enable DB construction to still work even after
    changes in schemas etc at UCSC, and ensembl sources.

    o bug fixes to makeFeatureDbFromUCSC allow it to work more
    reliably (it was being a little too optimistic about what UCSC
    would actually supply data for)

