Show appropriate message on error

When there was a malformed date in a file, spatialize did not show the
line number properly, because it was expecting a ValueError instead of
an iso8601.ParseError.
Fix spatialize inability to cope with file format

Spatialize assumed that the time series files are in text format (i.e.
without headers), but they can also be in file format. It now also
ignores empty lines.
Merge branch 'master' into 0.10
Version 0.10a13