added function to calculate super set, in change_bin.R
deleted change_bin and created a simpler function change_data that does most of the same
first pass at replacing change_bin with change_data in ss3sim_base
Documentation tweaks
Remove extra )
Paste an "a" instead of "l" for age bins
Re-document
Rename change_bin test file
Simplify dummy data return statements

Easier to test if not invisible; no need for return()
Add a section in the vignette about data changing
Add missing len_bins and age_bins

We may want to change how this works
Re-wrap the documentation in RStudio
Re-document
Remove an extra line
Remove old bin_params argument
Add the word "numeric", that's it
Fix a bunch of documentation
Remove pop_bins argument

It's not doing anything, right?
Remove old documentation on change_data
Add new bin argument documentation