Add utf8 charset explicitly to table definitions

[andynu]

For any databases that do not have utf8 as the default. Without this
setting the tables are created with the default, but are treated as
utf8, which can result in errors:

ERROR 1366 (HY000): Incorrect string value: '\xE2\x84\xAF\x0A -...' for column 'response_body' at row 1

This came up in the context of a legacy MySQL application.
The kind of project where this project is exceedingly useful!

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[hschne]

Excellent fix, thanks for submitting this! 🙌