Allows to customize the rendering function.

[jails]

After some investigation, I created a custom "vdom/create-element.js" function to catch the node creation step and to be able to perform some custom tasks. However I realized that there was a hard coded reference of the default "vdom/create-element.js" rendering function in "vdom/patch-op.js" and I didn't find a way to inject my custom rendering function.

In this PR there is a minor change which make the rendering function customizable the same way the patch function is.

Is it something acceptable ?

[coveralls]

Coverage increased (+0.0%) to 97.5% when pulling 87c61fa on jails:make-rendering-customizable into 1186cdc on Matt-Esch:master.

[dylanmcdiarmid]

👍

[Matt-Esch]

I'd love to merge this, I think it's the right way to go, but not without a test ;)

[jails]

No big deal, just squashed the commits.
I think the tests now cover all differents use cases.

[coveralls]

Coverage increased (+0.0%) to 97.5% when pulling 519fd8d on jails:make-rendering-customizable into 1dda0f6 on Matt-Esch:master.