ssGSEA: enrichment score calculation using normalized rank.expression data

[zqfang]

bug here, need to be fixed

[zqfang]

• add sample_norm_type argument to handle rank method
  see reference of ssGSEAprojection: https://github.com/GSEA-MSigDB/ssGSEAProjection-gpmodule/blob/master/src/ssGSEAProjection.Library.R
• scale ES by gene number to make it range between -1 and 1
  see reference from here: https://gist.github.com/gaoce/39e0907146c752c127728ad74e123b33

close now