Truncate address-related params before sending to Orbital

Orbital rejects fields that are too long with an error. So, presumably
they don't mind if part of the address is clipped so they'll at least
attempt to process it.

The maximum lengths are in the gateway
specification at http://rafeekphp.files.wordpress.com/2009/04/orbital-gateway-interface-specification-43.pdf.
Merge pull request #627 from jstorimer/orbital-max-length

Truncate address-related params before sending to Orbital