Bug 863066: Check for error in confirm task

In confirm_user task, add a check that we got a user_data object,
but it showed an error. Log the error and raise the right exception
so our task framework will retry.

Also add a few tests for this task, which didn't appear to have any
tests previously.
Merge pull request #50 from dpoirier/bug-863066-check-error-in-confirm-task
Bug 863066: Always fetch at least one ET field

Just guessing at why we're getting a weird error from ET - try
ensuring when we do a get_record(), we're always asking for at
least one field.
Merge pull request #51 from dpoirier/bug-863066-always-retrieve-at-least-one-field
Bug 863066: More logging when retries exhausted

Add more info to the exception that tasks raise when they hit
an error we should retry, so that if retries are exhausted and
the exception is propagated upward, there's information about
what that error was.
Merge pull request #52 from dpoirier/bug-863066-more-logging-when-retries-exhausted
Use lowercase lang codes in welcome message ids.
Merge pull request #53 from pmclanahan/lc-lang-code-welcome
Bug 863066: Fix subscription data returned

There was a bug in how we translated from what Exact Target gives us
to our preferred internal representation of what newsletters the user
is subscribed to. The symptom was that when a user confirmed, we
thought they hadn't subscribed to anything and so didn't send any
welcome messages.