Preview release - full IOOS SOS compatibility

Initial release that is compatible with all IOOS SOS services.

Requires yet-to-be released modification to pyoos for additional 'metadata_plus_exceptions' function in IoosSweSos collector: ioos/pyoos#71.

Some example calls to various SOS services:

sensorml2iso -s http://opendap.co-ops.nos.noaa.gov/ioos-dif-sos/SOS --verbose --response_formats='text/csv,text/xml;subtype="om/1.0.0/profiles/ioos_sos/1.0"'

sensorml2iso -s http://sdf.ndbc.noaa.gov/sos/server.php --verbose --response_formats='text/csv,text/xml;schema="ioos/0.6.1"'

sensorml2iso -s http://data.nanoos.org/52nsos/sos/kvp --verbose