Modify RISP_data() to return all bins in the file

[kaelyndunnell]

          I noticed that there is a difference across pulse types here. For FP, `data` contains all bins (hence we need to use `[bin_index]`. This is not the case for RISP.

We can maybe simplify this function greatly if we modify the RISP_data() method to return the whole dataframe (for all bins in the file) and not slice it. At least this would make this more understandable

Originally posted by @RemDelaporteMathurin in #64 (comment)