get pandas to try and detect the date
remove convert_objects
add infer_datetime_format
avoiding reparsing file for each date column when calculating temporal

still have to parse the file twice though.
simply date detection
only use our custom parser when we know which columns are dates

Although pandas default one uses dateutil, it's wrapped with other code
so that it handles errors more gracefully.
temporal extent error handling
Add some more metadata viewer tests
Don't crash when uploading a non-CSV file
Don't crash when previewing a non-CSV file
infer_schema_from_csv: better error checking
Merge branch 'master' of github.com:ckan/ckanext-b2 into date-type-autodetection

Conflicts:
	ckanext/datapackager/lib/csv_utils.py
	ckanext/datapackager/tests/lib/test_csv_util.py
Rename a couple of variables

Variableames buffer and type were overriding Python builtins
Delete an unnecessary # TODO comment
Merge branch 'date-type-autodetection'
try to check that the uploaded file is at least a text file

catch csv errors when infering schema that pandas may throw
catch validation errors thrown by action functions in helpers
Merge remote-tracking branch 'origin'
fix non csv warning test
fix viewing of unicode csv files