readme: Update failover setting names (#74)

README.md

@@ -350,7 +350,7 @@ status. When the task confirms that ReadySet is available again, it allows
 queries to be routed to ReadySet again.
 
 This feature is disabled by default. To enable it, set the
-`config.enable_failover` configuration option to `true`. You can read about the
+`config.failover.enabled` configuration option to `true`. You can read about the
 other available configuration options [here](#configuration-options).
 
 ## Configuration Options
@@ -363,16 +363,16 @@ The values below are the default values for each of the options.
 ```ruby
 Readyset.configure do |config|
   # Whether the gem's automatic failover feature should be enabled.
-  config.enable_failover = false
+  config.failover.enabled = false
   # Sets the interval upon which the background task will check
   # ReadySet's availability after failover has occurred.
-  config.failover_healthcheck_interval = 5.seconds
+  config.failover.healthcheck_interval = 5.seconds
   # Sets the time window over which connection errors are counted
   # when determining whether failover should occur.
-  config.failover_error_window_period = 1.minute
+  config.failover.error_window_period = 1.minute
   # Sets the number of errors that must occur within the configured
   # error window period in order for failover to be triggered.
-  config.failover_error_window_size = 10
+  config.failover.error_window_size = 10
   # The file in which cache migrations should be stored.
   config.migration_path = File.join(Rails.root, 'db/readyset_caches.rb')
 end