Fix docs in ReadTheDocs

[ljvmiranda921]

Minor fixes in our documentation in ReadTheDocs. We can merge to master and do
a patch release to update.

You can check if everything is working by making a local build:

$ cd pyswarms/docs
$ make html

Then go to _build directory, and open index.html in your browser.

Note: Make sure that the Sphinx package is installed.

Description

• Some examples have missing code blocks. We should use code-block instead of code
• Decided to separate Tutorials and Use-cases. Tutorials are for understanding the pyswarms API, Use-cases are applications in different fields, etc.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[ljvmiranda921]

Check this one first @whzup and if it's all good we can do 0.3.1 patch release 👍

[whzup]

Looks good to me!