Update RNA-seq Ortholog Mapping Analysis: Use a Results Table

Per [@jashapiro's comment](https://github.com/AlexsLemonade/refinebio-examples/pull/267#pullrequestreview-509594046) on PR #267 handling the addition of the RNA-seq ortholog mapping analysis to the repo, we will likely want to update this example analysis to show how to use it in the context of some other results: i.e a DE results table for which a user may want to see what the orthologs were.

The idea here would be showing the ortholog mapping example in a different context that is also not so _excessive_ as a full gene expression matrix.

Feel free to leave any additional thoughts on updating this analysis to show users ortholog mapping in a different context from the [microarray example](https://github.com/AlexsLemonade/refinebio-examples/blob/master/02-microarray/ortholog-mapping_microarray_01_ensembl.Rmd).

Start with the RNA-seq ortholog-mapping analysis added through PR #267 and compare it with 02-microarray/ortholog-mapping_microarray_01_ensembl.Rmd. Confirm how a DE results table can be used instead of a full gene expression matrix, then update the example so it demonstrates ortholog mapping in that context.

Written by the indexing model from the issue text.