---+ Build Tree
Build out the default tree and set the root of the tree with the super secret xprv CBHD key.
And the purpose of the Tree module is to function as a kind of wallet. So, in effect, we are testing the wallet code.
The reason that it is called the Tree module instead of a Wallet module is because the data structure of the BIP32 Hierarchial Deterministic keys reflects that of a tree.