Feature/tail compression

Hi Sean, I think this branch is ready to be merged in. I wrote a script to run a basic test and return simple numeric output for easy checking. This can be sourced by the `run_tests` script, which would be a good place to source future tests as well.

Further, I ran preliminary tests across a gradient of tail compression for the cod model and some old base case files. It performs well, indicating to me that the function and associated changes to the `run_ss3sim` and `ss3sim_base` functions are working properly.

Lastly, the `devtools::run_examples` executing without error. I did have some TeX issues with the CRAN check, but I think that's on my end. Have a look at see if you think it's ready.