* [ ] Return proper error codes from load_file()
    * Invalid header/magic
    * Bad MAC (password)
    * IO Error
    * Corrupt XML
* [ ] Document all the things
* [ ] Finish write support
    * [ ] Support customizing KDF
* [ ] Finish KDB1 support
    * [ ] Support working with KDB1 directly
    * [ ] Convert KDB1 to KDBX
    * [ ] Validate header hash