#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.
docs
Merge branch 'master' of github.com:monarch-initiative/monarch-app
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
Merge branch 'master' of github.com:monarch-initiative/monarch-app
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 'master' of github.com:monarch-initiative/monarch-app
Merge branch 'refs/heads/master' into pheno-gene-tab
Merge branch 'refs/heads/master' into pheno-gene-tab
Added documentation to JS scripts
Added documentation for CSS files
Merge branch 'refs/heads/master' into pheno-gene-tab
Added literature tab documentation to api.js
added hints option for determining type of id in disease-pheno query