Improve cells performance

[mostafa-sakhiri]

This is related to #12 .
The utils method cssStyleify is not scalable when displaying many cells.
Indeed, the method do the following on every cell

• Introspect each object to get the keys
• Instantiate a new array
• Iterate over the hash object
• Try to dasherize the key
• HtmlSafe the returned string

This leads to a lot of memory management operations (including garbage collection phases) for the JS VM and it's very slow.
We can get a significant performance gain by bypassing cssSyleify in this case.

[alexander-alvarez]

*since it leads to

[mostafa-sakhiri]

done. You are welcome.

[alexander-alvarez]

Thanks for this 👍

[mostafa-sakhiri]

To be more clear about the performance gain that we got :
In our context, we have an ember-light-table@1.12.2 on ember@2.4.6 with 300 cells (50 rows / 6 columns), and it's too slow (~9600 ms).
When implementing the solution above we gained a 33% of performance.

[alexander-alvarez]

Yeah, performance has been a problem area that we're always looking to improve on.

This addon has slowly been integrating vertical-collection that also helps with the problem (you can see the example code here http://offirgolan.github.io/ember-light-table/#/cookbook/occlusion-rendering). Basically with it we only render the rows that a user could see, instead of the whole table, and dynamically updates what's rendered as you scroll