webby numbers, simpler and faster

simpler because only two functions, is_prime() and is_webby() are used to find if a number is webby number.

faster because i have used global dictionaries to store prime and webby check results (True/False). This eliminates the need to recalculate something that was already run through any of the above two functions.

the results are significantly faster, with an increase of ~30x time as compared to the previous increase of ~50x time between the calls for 100 and 300. but is still slow.