This approach is a bit strange to read the first few time but has advantages in that it is easier to get right and faster to execute.
The interactions between `and`, `or`, `not`, and `()` can get confusing for new coders. For example, the code line 308 does not match the comment on 307 and I believe that in this case the comment correct and the code is wrong (for values < 200) because it is missing parens. I believe that __200 <= status_code < 300__ produces the correct results in a readable (semi-)intuitive code.
```
>>> for status_code in (-1, 1, 199, 200, 201, 299, 300, 301, 1000):
... print(not status_code >= 300 or status_code < 200,
... not (status_code >= 300 or status_code < 200),
... 200 <= status_code < 300)
...
True False False
True False False
True False False
True True True
True True True
True True True
False False False
False False False
False False False
```
Previously, there was a problem with sites that redirect an attempt to view a non-existing username to the main site. For example, if you try to go to https://devrant.com/users/dfoxxxxxxxxx (a user name that does not exist), then we get a redirect to the https://devrant.com/ root of the site. But, the "response_url" checking algorithm was only looking for the configured error URL being included in the response. So, these sites always indicated that the username was not found.
Update the "response_url" detection method so that the request does not allow redirects. If we get a 200 response of some type, then the username has been found. However, if we get something like a 302, then we know that the username was not found as we are being redirected.
This whole method seems fragile, but I did exhaustively test all of the supported sites, and they all work. So, this change is clearly an improvement.
Sherlock has a cool logo so this PR moves it to the top of sherlock.py to show it off when potential contributors read our source. It also makes a BANNER an __r'string'__ so we do not need backslashes to escape characters and the ascii art is more what-you-see-is-what-you-get. This also suppresses [a bunch of flake8 complaints](https://travis-ci.com/TheYahya/sherlock/jobs/172028552#L490-L503) about _invalid escape sequences_. Finally this PR runs isort on the imports for readability. Standard Lib imports come first, etc.
