IFrame plugin: Nested HTML table throws an error

[R.Brown]

Describe the bug
IFrame plugin: Nested HTML table throws an error in most of the browsers; e.g. Chrome, Safari

To Reproduce
Test https://io.labs64.com/guidechimp-iframe-plugin/ with the different browsers.

[Rudkovskiy]

PR: #68
PR: https://github.com/Labs64/GuideChimp-plugins/pull/3