Update .travis.yml

[AndersonMartins1]

Here are the changes made to the original code:

Added comments: Comments have been added to each section of the configuration file to explain its purpose and functionality. This helps developers understand the purpose of each step in the build process.

Improved readability: The code has been formatted for improved readability by adding indentation and breaking long lines into multiple lines where necessary. This makes it easier to follow the flow of the configuration file.

Clarified commands: Some commands have been clarified with comments to explain their purpose. For example, comments have been added to explain the purpose of installing Ruby version 2.3.0 and updating Pods for the Example project.

Language specification: The language used in the project (Objective-C) has been explicitly specified at the beginning of the file for clarity.

Overall, these changes enhance the clarity and understandability of the Travis CI configuration file.