Also sometimes it infers -gamma_1 insted of gamma_1.

The last version of the code is working well as illustrated in #5 .

I'll try to reproduce the issue I had above. In this scenario there were to calls to the model, which may trouble the code idk...

with ed.tape() as true_params:
    ims = model(N*N, stamp_size)

# Apply a constant shear on the field
custom_shear = [0.01, 0.]
with ed.condition(hlr=true_params['hlr'],
                  gamma=custom_shear,
                  e=true_params['e'],
                  ):
    ims = model(N*N, stamp_size)

This pull request contains a lot of code a files, but can be summarized as follow:

• refactor the code as a package
• gems/ed_utils.py enables batch computation through edward likelihoods
• gems/models.py contains all the probabilistic models that I implemented so far (we may want to split this file into pieces in the future)
• gems/psf.py is a utils file to get some psf models (not used in the latest PGM where we provide the PSF as input to the model, but needed for other scripts as scripts/simpler_model.py)
• gems/shear.py contains code modeling the shear at the map level assuming a GRF prior
• gems/utils.py utils code, mostly for the shear map model
• scripts/cosmo_shear_paramtric.py and scripts/cosmo_shear_real.py are scripts running inference on PGM using sersic light profiles to fit observations with 1) real galaxies 2) parametric galaxies
• scripts/simpler_model.py script to demonstrate model bias on observations generated with light profile only (e.g. gaussians on gaussians, gaussians on sersics, ...)
• scripts/varying_shear_gaussians.py is a script to perform inference using a PGM with a shear GRF prior

Merging this pull request would close the following issues:

• Toy model #1 #1 which describes how we set prior models for light profiles galaxies based on the COSMOS catalog sersic fit
• Shear inference with Gaussians #5 where we wanted to demonstrate that we could recover unbiased contours of the shear using gaussian light profile on gaussian galaxies observation
• Demonstrating model bias for realistic galaxies #11 describing experiment results fitting parametric models to both real and parametric galaxies, demonstrating model bias on real galaxy observations