#426 fetches genes that are associated to diseases and builds gene_associations object

Now calls fetchDiseaseGeneAssociations on every disease associated with the phenotype.

My main problem with this is the load time is ridiculously long. In the case of /phenotype/MP_0001322, we had to fetch the genes associated with 412 diseases, and now the gene_associations table is 1838 elements long.

I am considering cutting off the results after 1000. I may also need to use a different fetch function.
Merge branch 'refs/heads/master' into pheno-gene-tab
Merge branch 'refs/heads/master' into pheno-gene-tab
Added function for fetching DiseaseGeneAssocs

Checks cache for disease before calling fetchDiseaseGeneAssociations.
Merge branch 'refs/heads/master' into pheno-gene-tab

Conflicts:
	lib/monarch/api.js
fetchDiseaseGeneAssocsInfo currently fetches null objects (need to fix)
Merge branch 'refs/heads/master' into pheno-gene-tab
#426 Gene tab created

To Do:
1. Add genes associated with phenotypes by genotype-phenotype association.
2. Limit number of diseases (and genotypes) fetched by significance of phenotype to disease/genotype. (Need association strength score of some sort for this.)
#426 Added gene references to literature tab

To Do:
1. I noticed a bug where many diseases return duplicate genes. I need to filter for when I've already seen a gene.

Question:
1. What should I do if a gene is inferred from more than one disease-phenotype association? Should I combine all the associations or keep them separate?
Merge branch 'refs/heads/master' into pheno-gene-tab
Merge branch 'refs/heads/master' into pheno-gene-tab
Merge branch 'refs/heads/master' into pheno-gene-tab
Added literature tab documentation to api.js
#426 unique results for gene tab in phenotype page

Completed:
1. Passes through uniquifyResultSet function.
2. Limits iteration to 30 diseases. (Arbitrary to increase runtime.) Should be temporary till Nicole finishes function to calculate association strength of diseases and phenotypes.
Merge branch 'master' of https://github.com/monarch-initiative/monarch-app