argon2.parsehash: no attribute 'salt_len'
*Created originally on Bitbucket by Anonymous*
The `parsehash()` function for argon2 raises an exception:
```
#!python
argon2.parsehash(argon2.hash('foobar'))
```
raises `AttributeError: 'argon2' object has no attribute 'salt_len'`
issue