Ruby fix execute script, and fix constants generation

[ismasan]

In this PR:

• Update Ruby constants template, regenerate constants and fix code.
• Fix #execute_script to use data-effect="el.remove()" instead of onload="this.remove()"
• Document build task so that I don't forget about it next time.

[bencroker]

Looking good! One thing to change is that the attribute default should be empty.

[ismasan]

@bencroker I've removed that attribute default check since it's not needed anymore.

[bencroker]

Thanks!