Attempt to merge two data files and save then as .h5
Merge pull request #20 from jsantoul/master

attempt to merge pop.csv and pop.h5
Reproducing C Bonnet's work with truncated data.

Results are plausible. Two downsides for now :
unborns in 2007 have a lower net_transfer present value than the 2007 newborns. Need to identify where this discrepancy comes from.
New method of Cohorts() : compute_ipl.

The method has to be reviewed to check if nothing has been forgotten for the calculation of the IPL.
Merge pull request #21 from jsantoul/master

Attempt to recreate C Bonnet's work with truncated data
compute_ipl method fixed

One has to submit only cohorts with aggregated values in order to computes the IPL.
Added plots in Carole_Bonnet2.py
Expanded pyplot part of C_Bonnet2.py

Imported data from Carole Bonnet to compare with our results
The .xls file containing Carole's data
Merge pull request #22 from jsantoul/master

Expanded pyplot part of C_Bonnet2.py
Resolve conflicts