Refactor data() to return list of 1d DataFrames with namedtuples as columns.
refactorings. It has bugs.
More refactoring. Now data()can return a list of series with namedtuple as name. concat and status don't work yet. Don't use sdmx-2.0 yet.
Allow data to ge written to, and read from local file. Thus  one can work offline.
concat works except that namedtuples become tuples, perhaps due to a bug in pandas. with_status does not work yet. Fix from_file and to_file; use pd.to_dates instead of sdmx.date_parser.
Add option to convert list of series to multi-indexed DataFrames, discard obs_status for now. Testing needed.
merge from widukind
Sort index levels according to the number of values, largest first, refactor make_dataframe method.
Move all code from make_dataframe into data method. More refactoring.
Also sort keys when creating series_list. So do not keep order from the xml file. The order conveys just more info on the data.
start to refactor query_rest. Buggy.
Merge pull request #19 from dr-leo/initial_namedtuples

Return multi-indexed DataFrame, load data from, and save it to local file, many other improvements