fix(waf) : handle waf log format

[adrien-goetz-wmx]

#42

I add two options to fix 2 bugs I found when running the script.

N°1 : --convert_date

Traceback (most recent call last):
File "/Users/adrien/cloudgrep/cloudgrep.py", line 3, in
main.main()
File "/Users/adrien/cloudgrep/cloudgrep/main.py", line 69, in main
CloudGrep().search(
File "/Users/adrien/cloudgrep/cloudgrep/cloudgrep.py", line 117, in search
matching_keys = list(
^^^^^
File "/Users/adrien/cloudgrep/cloudgrep/cloud.py", line 186, in get_objects
if self.filter_object(obj, key_contains, from_date, end_date, file_size, convert_date=convert_date):
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/Users/adrien/cloudgrep/cloudgrep/cloud.py", line 246, in filter_object
if from_date and last_modified < from_date:
^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: can't compare offset-naive and offset-aware datetimes

I force conversion of from_date, end_date and last_modified variables using pytz

N°2: --use_og_name

When deciding if file should be uncompressed, script looks for .gz extension in tmp_name file generated by tempfile and not in original bucket key