Convert PyCola output to TFRecord

[YHRen]

PyCola produces a 3D universe (npz format)
We need to slice it into smaller trunks and convert it to TFRecord so that GAN can read it.

[YHRen]

reformatNBody.py requires refactoring...

• providing sensible API, removing hard-coded numbers, hard-coded directories and so on...
• remove the feature of producing histogram...

[YHRen]

io_Cosmo-3param.py convert npz to TFrecord.

[YHRen]

in cosmoGAN paper: "these simulation boxes were rotated and translated to produce 1000 ray-traced lensing maps at the redshift plane z=1.0. Each map covers 12 square degrees, with 2048x2048 pixels, which we downsampled to 1024x1024 pixels."
I need to find the code converting the 3D simulation boxes to 2D projections.