Release 2.8.0

[scls19fr]

Hello,

Like I said in #78 we need to define a release procedure.
I'm considering the following expected features and changelog (when PR merged)

https://github.com/scls19fr/python-semver/blob/402984a04efbba1c2c3b670fcd9c6869b8429063/CHANGELOG

A possible release procedure (in a release-procedure.md file) could be as defined in #81

Any comment?

[k-bx]

LGTM

[scls19fr]

Will do tomorrow afternoon

[scls19fr]

Github release tag https://github.com/k-bx/python-semver/releases/tag/2.8.0

[scls19fr]

https://pypi.org/project/semver/ is updated.

FYI, I modified my .pypirc

from

[distutils] # this tells distutils what package indexes you can push to
index-servers = pypi
    pypi # the live PyPI
    pypitest # test PyPI

[pypi]
repository:https://upload.pypi.org/legacy/
username:mypypi_login
password:*******

[pypitest]
repository:https://test.pypi.org/legacy/
username:mypypi_login
password:*******

to

[distutils] # this tells distutils what package indexes you can push to
index-servers = pypi
    pypi # the live PyPI
    pypitest # test PyPI

[pypi]
repository:http://pypi.python.org/pypi
username:mypypi_login
password:*******

[pypitest]
repository:https://testpypi.python.org/pypi
username:mypypi_login
password:*******