replace exessive "or"s with commas. (#3349)

* replace exessive "or"s with commas.

* replace exessive "or"s with commas.

* Add one more comma before the end of the list.

* Missed one.

Author: MichaelHinrichs

user/tutorial.md

@@ -14,8 +14,8 @@ instead.
 
 To start using Travis CI, make sure you have:
 
- * A [GitHub](https://github.com/) or [Assembla](https://www.assembla.com/) or [Bitbucket](https://bitbucket.org/) or [GitLab](https://about.gitlab.com/) account.
- * Owner permissions for a project hosted on [GitHub](https://help.github.com/categories/importing-your-projects-to-github/) or [Assembla](https://articles.assembla.com/en/articles/1665737-advanced-user-permissions-controls) or [Bitbucket](https://confluence.atlassian.com/bitbucket/transfer-repository-ownership-289964397.html) or [GitLab](https://www.tutorialspoint.com/gitlab/gitlab_user_permissions.htm).
+ * A [GitHub](https://github.com/), [Assembla](https://www.assembla.com/), [Bitbucket](https://bitbucket.org/), or [GitLab](https://about.gitlab.com/) account.
+ * Owner permissions for a project hosted on [GitHub](https://help.github.com/categories/importing-your-projects-to-github/), [Assembla](https://articles.assembla.com/en/articles/1665737-advanced-user-permissions-controls), [Bitbucket](https://confluence.atlassian.com/bitbucket/transfer-repository-ownership-289964397.html), or [GitLab](https://www.tutorialspoint.com/gitlab/gitlab_user_permissions.htm).
 
 ## To get started with Travis CI using GitHub