WIP Add wallet transactions route, view

Adds a new component for the wallet summary as well, and makes the
component tests work with RSpec.

app/views/wallet/transactions.html.erb

@@ -0,0 +1,11 @@
+<%= render HeaderComponent.new(title: "Wallet") %>
+
+<%= render MainSimpleComponent.new do %>
+  <%= render WalletSummaryComponent.new(balance: @balance) %>
+
+  <section>
+    <h3>Transactions</h3>
+
+    <p>Foo</p>
+  </section>
+<% end %>