[FIX] Update values of oxidation states

[lmmentel]

Fixes #199

Proposed Changes

• update values of oxidation states
• sort values before returning

Updated values:

>>> from mendeleev.fetch import fetch_table
>>> ox = fetch_table("oxidationstates")
>>> print(ox.head(25).to_string())
    id  atomic_number  oxidation_state  category
0    1              1                1      main
1    2              1               -1      main
2    3              3                1      main
3    4              4                0  extended
4    5              4                2      main
5    6              4                1  extended
6    7              5               -5  extended
7    8              5                2  extended
8    9              5                3      main
9   10              5                0  extended
10  11              5               -1  extended
11  12              5                1  extended
12  13              6               -1  extended
13  14              6               -2  extended
14  15              6                0  extended
15  16              6                1  extended
16  17              6                4      main
17  18              6               -4      main
18  19              6                2  extended
19  20              6                3  extended
20  21              6               -3  extended
21  22              7               -3      main
22  23              7                2  extended
23  24              7               -1  extended
24  25              7                5      main