Remove maintainer_name and maintainer_email

The current default of having a dedicated option for the maintainer is a
bit annoying:

  - If someone is using a cookiecutter template, they are most likely
    starting a new project, which means they are both the author and the
    maintainer. In this case, only author needs to be set.

  - The current default of null doesn't entirely work, and you're left
    with things like `__maintainer__ = 'None <None>'` in a few places.
    Having to remove these by hand is a little tedious.

To keep with the minimalism, this commit just removes the option to set
maintainer_name and maintainer_email.

{{cookiecutter.package_name}}/setup.py

@@ -8,11 +8,6 @@ setuptools.setup(
     author="{{ cookiecutter.author_name }}",
     author_email="{{ cookiecutter.author_email }}",
 
-    {%- if cookiecutter.maintainer_name -%}
-    maintainer="{{ cookiecutter.maintainer_name }}",
-    maintainer_email="{{ cookiecutter.maintainer_email }}",
-    {%- endif %}
-
     description="{{ cookiecutter.package_description }}",
     long_description=open('README.rst').read(),