Fix code action range

[Shane-XB-Qian]

take account 'range' to 'code action', i think it is a general spec way.

closes #71

[Shane-XB-Qian]

my PR should be mostly working, but i noticed there are 2 issues in following example:

1. the last line, the 'a', it is a 'unsafe' fix, but not sure why it listed in 'fix all';
2. if chose to apply this 'fix all' at that, the range seems was incorrect.

i donot know if it was me made it, or it was a known/existed bug,
@jhossbach not sure if you'd like this proposal also, if not, then let it be,
// if so, 'fix all' always be there, and seems following 2 issues would be covered also.

import os

b = c

def f():
    a = 2