#14 Support for on-disk bitmap indexes

[mason_s]

On-disk bitmap indexes may be helpful for performance in some cases. With the improvements to PostgreSQL 9.4's GIN indexes, both in size and performance, bitmap index support could be less important, as described here:

http://hlinnaka.iki.fi/2014/03/28/gin-as-a-substitute-for-bitmap-indexes

It may make sense to wait and only add support if bitmap indexes make it into the PostgreSQL itself.