How to get a score of 100 #160

Hey Max,

First off, thanks for creating/maintaining this awesome library !

I've been trying to find a way to get a score of 100 when comparing the strings 'simplee worde' and 'very simple big word'. Knowing that that:

>>> fuzz.partial_ratio('simplee','simple')
100.0
>>> fuzz.partial_ratio('worde','word')
100.0

By reading the docs, I thought that partial_token_set_ratio would work but it didn't.

>>> fuzz.partial_token_set_ratio('simplee worde','very simple big word')
69.23076923076923

I assume that's because there are no perfectly similar words between both ? (if i put simple instead of simplee it gives me 100)

Also, I found out that by adding letters after the worde increased the score to a cap of 75.00 but adding the letters to the end of the word simplee made the score drop to a lower limit of 55.17.

>>> fuzz.partial_token_ratio('simpleeadassdsdl worde','very simple big word')
55.172413793103445
>>> fuzz.partial_token_set_ratio('simplee wordeeaaasasdasd','very simple big word')
75.0

In case you're wondering, the other fuzz modules performed worse.

This is some strange behaviour that I don't understand because I don't know the underlying algorithms you're using.

Maybe you can shed some light here, and tell why, in this case, it's not possible to get a score of 100.