Merge pull request #9 from JesseWeinstein/fix_relationship_editing

First step towards fixing relationships editing after musicbrainz website changes:
New utility function that manages relationship editor seeding, and fix add_url by using this new function.
Fix pep8 E231: missing whitespace after ‘,’
Fix pep8 E203: whitespace before ‘:’
Fix pep8 E201 & E202: whitespace after ‘(‘ or before ‘)’
Fix pep8 E225: missing whitespace around operator
Fix pep8 E701: multiple statements on one line (colon)
Merge branch 'autopep8_changes' of github.com:JesseWeinstein/musicbrainz-bot into autopep8_changes