Add flag for ignoring SSL errors

[William Overton]

Describe the bug
When testing against an internal site with invalid SSL I get this error:
An error occured while fetching URL, Might be server is down, or domain does not exist, Please check!

Suggested Fix
Add a flag which ignores all ssl errors (-k in this example)

1. Have site with invalid ssl
2. Run python3 SubDomainizer.py -u -k https://mysite.com
3. ???
4. Profit

[Neeraj Sonaniya]

@williamoverton Let me know if this fixes the problem.