Add Money Transfer Services to list of Services on Profile

Currently, Bitcoin and Zcash are listed on user profiles, but no other means of money transfer are. Other services should be allowed.

Some services that might be supported are:

* Other cryptocurrencies
* PayPal (which is widely used)
* Google Wallet
* Square Cash
* Ethereum (which technically is a cryptocurrency, or a bunch of them together)
* Ripple

Some cryptocurrencies I'd like to see added are Monero (anonymity), Ethereum (it's revolutionary), Litecoin (because it is secure and established), and Primecoin (it helps find new primes and prime-chains, which can help with security in the future).

## How Would We Verify These Services?
Some services cannot be verified, but we can attempt to do so anyway.

### Cryptocurrencies
We could have a very small amount of the currency be sent to an address controlled by Keybase and have a message be sent with it if the currency allows it (Monero and some other currencies). Otherwise, just trust that it really is that person's address if it is registered with their account.

### PayPal

PayPal has one verify their bank account by sending something like $0.02 to the PayPal account. It may be possible to do the same with verifying PayPal to Keybase.

### Google Wallet

See **PayPal**.

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**Q:** Why should Keybase use these micropayments for verification?
**A:** These micropayments can be thought of as (very) small donations to Keybase and can be used as a small amount of funding for the service.
**Pro:** This helps fund Keybase.
**Con:** If the person has none of a currency (e.g., Bitcoin), they can't verify their address this way.

The issue names no files, tests, or entry points. Start by locating the profile services and verification flow, then narrow the supported payment services and define how each can be verified; done requires an agreed scope and working profile integrations.

Written by the indexing model from the issue text.