Revert "send all create requests using a POST request (untested, could break, ymmv etc...)"

This reverts commit 8652491295afe804668aa11bb2d9d93b4ebfece1.
fixing specs for changed put -> post
allowing parent to be nil for some Records (for testing purposes only).
switching fake application to nil in test
Fix setting the 'Class' attribute on Accounts.

If you try to set the 'Class' attribute on an account, you'll get a
NoMethodError about the method "class=" not existing. This patch will try
the straight key name first, and if that fails, fall back to the field's
internal name ('account_class', in this case).
Don't use POST on endpoints that don't support it.
Added URL field to BankTransactions.
Merge pull request #147 from fimmtiu/add-url-to-bank-transactions

Added URL field to BankTransactions.
Merge pull request #146 from fimmtiu/always-put-accounts

Don't Use POST on Endpoints That Don't Support It
Send the default headers in OAuth as well
Add new timezone field to organisation record

Xero added a timezone field to the organisation object, recently.
Add primary key to TaxRate to fix saving

We were having trouble saving `TaxRate` objects because the primary key was missing. This worked like a charm in our monkey patch.
Added archive status to contacts
Merge pull request #153 from warrenchaudhry/add_archive_status_to_contacts

Add Archive Status to Contacts
Merge pull request #150 from clodeindustrie/patch-1

Add Timezone Field to Organisation
change ARCHIVE status to ARCHIVED
Merge pull request #154 from warrenchaudhry/add_archive_status_to_contacts

Change ARCHIVE Status to ARCHIVED
add include_archived params for contacts
Merge pull request #155 from warrenchaudhry/add-include-archived-params

Add include_archived Params for Contacts
Add datetime_utc type to http_proxy

This allows fields of type datetime_utc to be used in where clauses.
The datetime_utc type was added in commit
cdae18e1694e3ce6aa9d333f3443f6d4591ad283 but was never added to
base_model_http_proxy, so you get empty where conditions when you
try to filter on fields of that type. This commit fixes that.