Adds 'zonmean' option to loaddata and a unit test.
Set loaddata to always use cdo, never nc4
Adds get_dimensions function to loaddata
Adds loadfiles method to loaddata, plus a test.

loadfiles loads the same variable (of arbitrary dimension) from
many files into an array, which it returns. loadfiles replaces
mload1d, which is now removed.
introduce classes in data.py
added mkensemble method, modified test
switched join_exp_slice methods to classes
Consolidated modules, fixed cat_experiments

All functions have been consolidated into three basic modules:

 - preprocessing_tools
 - loading_tools
 - plotting_tools

In preprocessing_tools major work was done on cat_experiments to
work with ensemble objects and to return an updated ensemble after
processing. Some minor adjustments were made to some classes to
allow for easier deletion of objects.
updated README
updated README
updated README
updated README
updated README
updated README
updated README
Updates preprocessing, loading and plotting tools to class.

All methods in preprocessing tools now use the class based
structure. Methods time_anomaly and my_operator were added.

In loading_tools loadfiles was updated to the class based
structure.

Plotting tools were initialized with two functions, but these
are preliminary and need work.
update my_operator in preprocessing
Adds loadens and updates join_experiments.

loadens is an attempt to add data to the ensemble object.

join_experiments handled the case of overlapping experiment dates
incorrectly, because the cdo cat and seldate operators were joined
but should have been applied separately.
minor updates to time_slice and sinfo