Add a details section to explain argument requirements.
Change log-check "stop" to a warning, fix a change in first stop
Improve Zpep track for normalization. 
Adds a function to compute Z-scales from peptide sequences if Z-scale
values are not found in the featureRange slot of the peptideSet
argument.

Removes some redundant or unnecessary pieces of code and comments. 

Adds a check to the method argument.
Fix bug in how normalization data is added to "preproc" info.