Work with Confluence 7.5/MathJax 3.x

[Roland Roberts]

The plugin works with Confluence 7.5, but is listed as incompatible, so that seems trivial.

However, it gives the option of using a MathJax 3.x version, which doesn’t work because the cdnjs URL is wrong.

And…if you manually put in an URL for a 3.x version, the custom delimiters are no longer honored, going back to the defaults.

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[Scott Selberg]

Fixed in 3.1.1