Add gene list word cloud function

[Shians]

Idea for a toy function to display literature word cloud for a list of genes.

NCBI provides references for literature on specific genes: https://www.ncbi.nlm.nih.gov/gene/8404#bibliography

It should be possible, for an arbitrary list of genes, to scrape the literature and generate a word cloud to give a very high level overview of the gene's potential importance. Word cloud from R-blogs.