"d" and "h" swapped in compressed strings when using `«`/`»`

[kcruijss]

In math_golf.py lines 84 and 86 the strings are "etaoinsrhluczbfp" and "gwymvkxjqd_?*#.,", where the 'd' and 'h' are swapped in comparison to the docs. These strings should be compressed_letters_0 and compressed_letters_1 instead (the constant defined in helper_functions.py)