Updates travis to the .com domain (#553)

Any new project created would now land on the travis-ci.com domain.
https://blog.travis-ci.com/2018-05-02-open-source-projects-on-travis-ci-com-with-github-apps

Author: AndreMiras

{{cookiecutter.project_slug}}/.travis.yml

@@ -1,4 +1,4 @@
-# Config file for automatic testing at travis-ci.org
+# Config file for automatic testing at travis-ci.com
 
 language: python
 python:

{{cookiecutter.project_slug}}/CONTRIBUTING.rst

@@ -103,7 +103,7 @@ Before you submit a pull request, check that it meets these guidelines:
    your new functionality into a function with a docstring, and add the
    feature to the list in README.rst.
 3. The pull request should work for Python 3.5, 3.6, 3.7 and 3.8, and for PyPy. Check
-   https://travis-ci.org/{{ cookiecutter.github_username }}/{{ cookiecutter.project_slug }}/pull_requests
+   https://travis-ci.com/{{ cookiecutter.github_username }}/{{ cookiecutter.project_slug }}/pull_requests
    and make sure that the tests pass for all supported Python versions.
 
 Tips

{{cookiecutter.project_slug}}/README.rst

@@ -8,7 +8,7 @@
         :target: https://pypi.python.org/pypi/{{ cookiecutter.project_slug }}
 
 .. image:: https://img.shields.io/travis/{{ cookiecutter.github_username }}/{{ cookiecutter.project_slug }}.svg
-        :target: https://travis-ci.org/{{ cookiecutter.github_username }}/{{ cookiecutter.project_slug }}
+        :target: https://travis-ci.com/{{ cookiecutter.github_username }}/{{ cookiecutter.project_slug }}
 
 .. image:: https://readthedocs.org/projects/{{ cookiecutter.project_slug | replace("_", "-") }}/badge/?version=latest
         :target: https://{{ cookiecutter.project_slug | replace("_", "-") }}.readthedocs.io/en/latest/?badge=latest