Add computation graph based logistic regression

[Benardi]

Description

Add a computation graph based logistic regression

Files

• touvlo/supv/lgx_rg.py
• tests/supv/test_lgx_rg.py

Tasks

• [x] Implement a lgx_rg submodule using computation graph
  • Organize all lgx_rg modules to prevent naming clashes
• [x] Add documentations for implemented module
• [x] Add unit tests for implemented module
• [x] If necessary, reorganize existing modules to prevent that the calls to modules attributes are too deep: touvlo.X.Y.Z.W.attribute