SBA source has been switched to https.

If you hit the http URL you get redirected to https, which is fine
expect that the imported doesn't like this and throws an error.
Remove USTDA-specific mappings.

TradeEvent::Mappings already has them.
Merge pull request #57 from GovWizely/calum/remove-ustda-mappings-additions

Remove USTDA-specific mappings.
Added api v2 support