Update/ tutorial text

[schoinh]

Resolves: more tutorial revisions

Hmmmm.... I resolved Blair's updates as I went (hard to see the outcome of some formatting updates if I don't resolve), so they're not visible on the Google Doc anymore. But they were all updates to the second major bullet ("Convert your data into Simularium format").

Before:

After:

Pull request recommendations:

• Name your pull request your-development-type/short-description. Ex: feature/read-tiff-files
• Link to any relevant issue in the PR description. Ex: Resolves [gh-##], adds tiff file format support
• Provide description and context of changes.
• Provide relevant tests for your feature or bug fix.
• Provide or update documentation for any feature added by your pull request.

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