Add auto-deployment to PyPI

[khanhak]

We have added the requested feature to auto-deploy to PyPI by making the following changes
When the master branch is updated:

• We added the "deploy" attribute to the .travis.yml to add automatic deployment to PyPI
• We added the "after-test" attribute to .travis.yml to invoke the automatically deployment when all tests successfully pass
• We implement the creation of a new version number within the "after-test" deployment to PyPI, which was a requested feature

[erwanp]

Hello, you're using : AppVeyor : isn't this Windows-only ? Pytexit is tested on Travis-CI Linux machines.

Also, you removed the codecov deployment. Is there a reason ?

[erwanp]

Update on the questions above?