demo workflow readxl missing

[tobigithub]

Followed the step-by-step installation instructions, then used the demo workflow,
still got this error:

1) library(Retip)
2) prep.wizard() - Windows firewall warning (allow)
socket cluster with 72 nodes on host ‘localhost’
3) RP2 <- readxl::read_excel("Plasma_positive.xlsx", sheet = "lib_2", col_types = c("text","text", "text", "numeric"))
Error in loadNamespace(name) : there is no package called ‘readxl’

Potential solution, install

 install.packages("readxl")