Fix #8 build

[SrMouraSilva]

Fix #8

Notes

• Now install tensorflow < 2.0.0
  • Prevent a future broken
• Now install matplotlib < 3.0.0
  • Matplotlib 3 drops python 2.x support
• Add build;
  • Example: https://travis-ci.org/SrMouraSilva/boltzmann-machines/
• Add code coverage;
  • Example: https://codecov.io/gh/SrMouraSilva/boltzmann-machines/branch/issue-8-build
• Add setup_cpu.py to install tf without GPU
  • See README changes
• Add badges in README.md
• Use pytest instead nosetests;
  • Nosetests last commit is in 2016
• Use absolute imports
• Fix tests
• Fix python 3 examples support

How to configure continuous deploy:

• Create a account in Travis-CI with github account and enable boltzmann-machine repository;
• Create a account in Codecov with github account and enable boltzmann-machine repository;

[SrMouraSilva]

@monsta-hd, When running the tests, I came across a test that always fails. Is this expected?

TestRBM.test_consistency https://travis-ci.org/SrMouraSilva/boltzmann-machines/jobs/502665556#L1793