Add more timeout smarts

The timeout to talk to Spreedly is now much shorter in general.  The gem
is now smarter in that if the underlying api call actually talks to a
payment gateway, then the timeout is longer since some gateways can take
awhile to respond when they're under load.
Up the version
add find_transaction_transcript to environment
Refactor the ssl requester a bit

And up the version.
Handle response-less transaction

Some GatewayTransactions don't have a response because they failed
before we even spoke with the gateway.  We now handle this case more
gracefully.
Up the version
Add AuthMode class
Add credential class
Require auth mode and credential classes
Add auth_modes to gateway class, refactor indentation
Add auth mode name
Add auth modes and credentials tests
Parse credential safe field as boolean
Add a remote test for auth modes
Pass through verification_value

This is when you're adding a card directly without using the transparent
redirect.  Closes #19.
Bump version
Update history
implemented gateway characteristics
Allow access to gateway options w/o credentials
Merge pull request #26 from ilyutov/master

implemented gateway characteristics