Validator on-boarding docs (#656)

* Add first draft of validator onboarding

* Update docs

* Add documentation link to main README

* Continue docs development

* Update book readme

* Update docs

* Allow vc to run without testnet subcommand

* Small change to onboarding docs

* Tidy CLI help messages

* Update docs

* Add check to val client see if beacon node is synced

* Add notifier service to validator client

* Re-order onboarding steps

* Update deposit contract address

* Update testnet dir

* Add note about public eth1 node

* Set default eth1 endpoint to sigp

* Fix broken test

* Try fix eth1 cache locking

* Be more specific about eth1 endpoint

* Increase gas limit for deposit

* Fix default deposit amount

beacon_node/src/cli.rs

@@ -6,7 +6,9 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
         .visible_aliases(&["b", "bn", "beacon"])
         .version(crate_version!())
         .author("Sigma Prime <contact@sigmaprime.io>")
-        .about("Eth 2.0 Client")
+        .about("The primary component which connects to the Ethereum 2.0 P2P network and \
+                downloads, verifies and stores blocks. Provides a HTTP API for querying \
+                the beacon chain and publishing messages to the network.")
         /*
          * Configuration directory locations.
          */
@@ -187,7 +189,7 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
                 .value_name("HTTP-ENDPOINT")
                 .help("Specifies the server for a web3 connection to the Eth1 chain.")
                 .takes_value(true)
-                .default_value("http://localhost:8545")
+                .default_value("https://goerli.public.sigp.io")
         )
         .arg(
             Arg::with_name("slots-per-restore-point")