get_count_data_long: Creates long format count data.
In jminnier/shinysequin: Visualization of Sequencing Data with Shiny and ggvis.

Creates long format count data.

1	get_count_data_long(groupvec, id_vars, data)

`groupvec`	a character vector of group names (i.e. tissue type), assuming column names of counts include these characters
`id_vars`	a character vector of gene identifier column names
`data`	a data frame that includes counts and gene identifiers

1 2	mycountslong <- get_count_data_long(groupvec=c("tissueA","tissueB","tissueC"),data=countdata, id_vars = c("Geneid","MGIID","Chr")) head(mycountslong)