Starting on IPU implementation with function for the quality metric.
Function for calculating new household weights.
Add class for handling the frequency table in a sparse manner.
Add function for calculating average fit quality across all household/person types.
Add function that does the IPU iteration to get final household weights.
includes additional IPF functions and the popgen_test_run notebook for data prep, IPF, IPU
addition of test data to be used with popgen_test_run.ipynb
pep8 formatting update
moved test notebook to demos
removing old demo notebook
Merge pull request #3 from synthicity/ipu

popgen.ipu module addition of data preparation steps and ipf portion along with updated demo notebook