initial pass at DBStream and MySQLStreamer
first pass at mongostreamer
move to_vw up into BaseStreamer
make a few small logical changes to the two db streamers
write documention on database streamers
typo in requirement module
add tests for TextIterStreamer.  Fix error I had introduced
start of mysqlstremer test
added to mysql test
finished mysqlstreamer test
remove check for doc_id in .to_vw
add Mongo Streamer tests.  make sure they pass
fixing merge conflict with db_stream