minor xdefi issues

[Reid Rankin]

hdwallet-xdefi has a few miscellaneous issues:

• There are a few typos
• It imports all of lodash when only some is required
• Its integration tests' mocks affect the environment of all other wallets' tests
• It implements create()/info() functions which turn out to be unnecessary

AC:

• Fix typos
• Import only the lodash functions that are needed (i.e. lodash/isObject)
• Put the mocks in __mocks__ and use jest's automock functionality to apply them when nessecary
• Remove the create() and info() functions before anyone can get around to using them

Fixed by #423.