Fix NameError in delete_paste.

This fixes problem:
NameError: global name 'request_string' is not defined

when you call:
PastebinAPI().delete_paste(api_dev_key, api_user_key, api_paste_key)
Remove extra spaces.
Remove unused import.
Fix extra/missing spaces.
Fix lines to keep them below 80 characters.
Indentation fixes.
Remove unsed call to non-existing main().
Merge pull request #3 from ivanalejandro0/feature/pep8-fixes

Feature/pep8 fixes
Merge pull request #2 from ivanalejandro0/bug/request_string-is-not-defined

Fix NameError in delete_paste.