Add basic API docs (#15)

README.md

@@ -30,6 +30,91 @@ console.log(hdkey.publicExtendedKey)
 ```
 
 
+### `HDKey.fromMasterSeed(seedBuffer[, versions])`
+
+Creates an `hdkey` object from a master seed buffer. Accepts an optional `versions` object.
+
+```js
+var seed = 'a0c42a9c3ac6abf2ba6a9946ae83af18f51bf1c9fa7dacc4c92513cc4dd015834341c775dcd4c0fac73547c5662d81a9e9361a0aac604a73a321bd9103bce8af'
+var hdkey = HDKey.fromMasterSeed(new Buffer(seed, 'hex'))
+```
+
+### `HDKey.fromExtendedKey(extendedKey[, versions])`
+
+Creates an `hdkey` object from a `xprv` or `xpub` extended key string. Accepts an optional `versions` object.
+
+```js
+var key = 'xprvA2nrNbFZABcdryreWet9Ea4LvTJcGsqrMzxHx98MMrotbir7yrKCEXw7nadnHM8Dq38EGfSh6dqA9QWTyefMLEcBYJUuekgW4BYPJcr9E7j'
+var hdkey = HDKey.fromExtendedKey(key)
+```
+
+**or**
+
+```js
+var key = 'xpub6FnCn6nSzZAw5Tw7cgR9bi15UV96gLZhjDstkXXxvCLsUXBGXPdSnLFbdpq8p9HmGsApME5hQTZ3emM2rnY5agb9rXpVGyy3bdW6EEgAtqt'
+var hdkey = HDKey.fromExtendedKey(key)
+```
+
+### `HDKey.fromJSON(obj)`
+
+Creates an `hdkey` object from an object created via `hdkey.toJSON()`.
+
+---
+
+### `hdkey.derive(path)`
+
+Derives the `hdkey` at `path` from the current `hdkey`.
+
+```js
+var seed = 'fffcf9f6f3f0edeae7e4e1dedbd8d5d2cfccc9c6c3c0bdbab7b4b1aeaba8a5a29f9c999693908d8a8784817e7b7875726f6c696663605d5a5754514e4b484542'
+var hdkey = HDKey.fromMasterSeed(Buffer.from(seed, 'hex'))
+var childkey = hdkey.derive("m/0/2147483647'/1")
+
+console.log(childkey.privateExtendedKey)
+// -> "xprv9zFnWC6h2cLgpmSA46vutJzBcfJ8yaJGg8cX1e5StJh45BBciYTRXSd25UEPVuesF9yog62tGAQtHjXajPPdbRCHuWS6T8XA2ECKADdw4Ef"
+console.log(childkey.publicExtendedKey)
+// -> "xpub6DF8uhdarytz3FWdA8TvFSvvAh8dP3283MY7p2V4SeE2wyWmG5mg5EwVvmdMVCQcoNJxGoWaU9DCWh89LojfZ537wTfunKau47EL2dhHKon"
+```
+
+### `hdkey.sign(hash)`
+
+Signs the buffer `hash` with the private key using `secp256k1` and returns the signature as a buffer.
+
+### `hdkey.verify(hash, signature)`
+
+Verifies that the `signature` is valid for `hash` and the `hdkey`'s public key using `secp256k1`. Returns `true` for valid, `false` for invalid. Throws if the `hash` or `signature` is the wrong length.
+
+### `hdkey.toJSON()`
+
+Serializes the `hdkey` to an object that can be `JSON.stringify()`ed.
+
+```js
+var seed = 'fffcf9f6f3f0edeae7e4e1dedbd8d5d2cfccc9c6c3c0bdbab7b4b1aeaba8a5a29f9c999693908d8a8784817e7b7875726f6c696663605d5a5754514e4b484542'
+var hdkey = HDKey.fromMasterSeed(Buffer.from(seed, 'hex'))
+
+console.log(hdkey.toJSON())
+// -> {
+//      xpriv: 'xprv9s21ZrQH143K31xYSDQpPDxsXRTUcvj2iNHm5NUtrGiGG5e2DtALGdso3pGz6ssrdK4PFmM8NSpSBHNqPqm55Qn3LqFtT2emdEXVYsCzC2U',
+//      xpub: 'xpub661MyMwAqRbcFW31YEwpkMuc5THy2PSt5bDMsktWQcFF8syAmRUapSCGu8ED9W6oDMSgv6Zz8idoc4a6mr8BDzTJY47LJhkJ8UB7WEGuduB'
+//    }
+```
+
+### `hdkey.privateKey`
+
+Getter/Setter of the `hdkey`'s private key, stored as a buffer.
+
+### `hdkey.publicKey`
+
+Getter/Setter of the `hdkey`'s public key, stored as a buffer.
+
+### `hdkey.privateExtendedKey`
+
+Getter/Setter of the `hdkey`'s `xprv`, stored as a string.
+
+### `hdkey.publicExtendedKey`
+
+Getter/Setter of the `hdkey`'s `xpub`, stored as a string.
+
 References
 ----------
 - https://github.com/bitcoinjs/bitcoinjs-lib/blob/master/src/hdnode.js