txt2npy logical check for already existing files

[medwar99]

Hi, thanks for the converter to .npy extension. It looks like the logical check on line 123 wants to be checking if each+'.npy' in alread_exist_dict, rather than each+'.skeleton.npy'. For me it was always seeing (e.g.) 'S001C001P001R001A003.skeleton.skeleton.npy', and was always overwriting the numpy files.