januarharianto/respR: respR 1.0.5.1

This version is aimed at improving the functionality and usability of our conversion functions. We have decided to remove the default values for temperature and salinity inputs in convert_DO() and convert_rate() (i.e. switched t and S numerics to NULL). This was no easy decision, but we noticed that some users were running the functions by default without considering (or even knowing the existence of) these two important input variables. With this change, existing workflows using calc_DO() and calc_rate() are likely to break.

• NEW: Additional vignettes added. We now have a total of 15 vignettes!
• UPDATE: Refreshed existing vignettes.
• UPDATE: convert_DO() and convert_rate() now require the user to explicitly provide t (temperature) and S (salinity) values.
• UPDATE: convert_DO() and convert_rate() will warn the user when the default P value is used for O₂ units that are strongly influenced by atmospheric pressure.
• UPDATE: unit_args() has been updated to indicate which O2 units need inputs of t, S and P.
• FIX: inspect() has a better-looking plot for rolling regressions.