move xtra construction inside of vtec loop, add more tests
account for invalid "blank lines" by pre-cleaning all VTEC stuff
add more vtec info to the logged message
cleanups, more docs, and clarify/add some tests
Better support for flood SBWs

Attempt to account for some hair logic that occurs with flood SBWs, that
are in the future and can change forward and backwards in time.  This is
ugly, but should be okay with a test
better support for product corrections, add test
VTEC start and end times can be None, add test, bump version
fix spacing issue when vtec product starts in future
don't update previous SBW polygons in CAN state
Properly save SVS text to warnings_ table

Ugly bug with attempting to combine a null svs column with updated text
Fix some failing tests