keyring docs with more examples and FAQ (#68)

packages/ui-keyring/README.md

@@ -3,8 +3,10 @@
 A wrapper extending the base @polkadot/keyring interface for usage in the browser:
 Key management of user accounts including generation and retrieval of keyring pairs from a variety of input combinations.
 
-## Usage Example
+## Usage Examples
 All module methods are exposed through a single default export.
+
+### Regular
 ```
 import keyring from @polkadot/ui-keyring
 
@@ -21,8 +23,52 @@ render () {
 
   // save account from pair
   keyring.saveAccount(pair, password);
+
+  // save address without unlocking it
+  keyring.saveAddress(address, { ...meta });
 }
 ```
+### Observables
+```
+import React from 'react';
+import accountObservable from '@polkadot/ui-keyring/observable/accounts';
+
+class MyReactComponent extends React.Component {
+  componentDidMount () {
+    accountObservable.subscribe((observedAccounts) => {
+      this.setState({
+        accounts: observedAccounts
+      });
+    })
+  }
+
+  render () {
+    const { accounts } = this.state;
+
+    return (
+      <h1>All Accounts</h1>
+      {
+        Object.keys(accounts).map(address => {
+          return <p> {address} </p>;
+        })
+      }
+    )
+  }
+}
+```
+
+## FAQ
+- Difference between Keyring Accounts and Addresses?
+  - From the perspective of the keyring, it saves a particular user's unlocked identities as an account, a la keyring.saveAccount(pair, password). So with these accounts you are able to send and sign transactions.
+  - To save addresses without unlocking them (i.e. because a user might want to have easy access to addresses they frequently transact with), use keyring.saveAddress(address, meta)
+- What are 'external' accounts, i.e. when to set the `isExternal` meta key to true?
+  - An external account is one where the keys are not managed by keyring, e.g. in Parity Signer or Ledger Nano.
+- SS58 Encode / Decode?
+  -  SS58 is a simple address format designed for Substrate based chains. You can read about its specification in more detail in the [Parity Wiki](https://wiki.parity.io/External-Address-Format-(SS58)).
+
+**If you have any unanswered/undocumented questions, please raise an issue [here](https://github.com/polkadot-js/ui/issues).**
+
+
 
 ## Users
 Keyring is core to many polkadot/substrate apps.