Add CashRefunds & Associated Objects.

Only adding the fields that we need for now.
Added initial search support for Account Periods.
Add test for Records::AccountingPeriod.search
Adding memo field to CustomerDeposit
Add support for custom soap headers
Fix broken spec

The spec was originally broken by f39a156c8cf6c46f2c3e80e1b0fc2c2bf814b0f4
Remove test that never had implementation added for it. Added in 46d4de48c7a20cbe6ab82869a9d60ec7ff19bb92
Revert bad symbol rename

It was broken in 6a3aa7147a29b81f29f830ad87d78394e5e95171
Update broken spec

It was broken by 47ef116c43d1f97828fe74da4f13dd3820187d01
Version bump
Update README.md