Documentation Request for Using RSCU param with `python_codon_tables`

[HarryMWinters]

Just like it sounds. It'd be great to see how to use the RSCU param in the docs. In particular how to integrate it with the value from python_codon_tables.get_codons_table().

Most of the examples are using a reference genome and I get key errors when I try:

RSCU = python_codon_tables.get_codons_table("h_sapiens")
initial_grade = CAI.CAI(initial_seq, RSCUs=RSCU)