Fix default URL binding

The default binding for launching the URL hints was documented as
Ctrl+Shift+U, but never actually set. This adds this binding as the
default instead of having URLs only launchable using the mouse.
diff --git a/alacritty/src/config/mod.rs b/alacritty/src/config/mod.rs
index 4ddc81c..e2476bb 100644
--- a/alacritty/src/config/mod.rs
+++ b/alacritty/src/config/mod.rs
@@ -118,8 +118,7 @@
             config
         });
 
-    // Override config with CLI options.
-    options.override_config(&mut config);
+    after_loading(&mut config, options);
 
     config
 }
@@ -130,12 +129,20 @@
     let config_options = options.config_options().clone();
     let mut config = load_from(config_path, config_options)?;
 
-    // Override config with CLI options.
-    options.override_config(&mut config);
+    after_loading(&mut config, options);
 
     Ok(config)
 }
 
+/// Modifications after the `Config` object is created.
+fn after_loading(config: &mut Config, options: &Options) {
+    // Override config with CLI options.
+    options.override_config(config);
+
+    // Create key bindings for regex hints.
+    config.ui_config.generate_hint_bindings();
+}
+
 /// Load configuration file and log errors.
 fn load_from(path: &Path, cli_config: Value) -> Result<Config> {
     match read_config(path, cli_config) {
@@ -159,9 +166,6 @@
     let mut config = Config::deserialize(config_value)?;
     config.ui_config.config_paths = config_paths;
 
-    // Create key bindings for regex hints.
-    config.ui_config.generate_hint_bindings();
-
     Ok(config)
 }
 
diff --git a/alacritty/src/config/ui_config.rs b/alacritty/src/config/ui_config.rs
index d34389e..d1f16f8 100644
--- a/alacritty/src/config/ui_config.rs
+++ b/alacritty/src/config/ui_config.rs
@@ -2,6 +2,7 @@
 use std::path::PathBuf;
 use std::rc::Rc;
 
+use glutin::event::{ModifiersState, VirtualKeyCode};
 use log::error;
 use serde::de::Error as SerdeError;
 use serde::{self, Deserialize, Deserializer};
@@ -238,7 +239,10 @@
                 action,
                 post_processing: true,
                 mouse: Some(HintMouse { enabled: true, mods: Default::default() }),
-                binding: Default::default(),
+                binding: Some(HintBinding {
+                    key: Key::Keycode(VirtualKeyCode::U),
+                    mods: ModsWrapper(ModifiersState::SHIFT | ModifiersState::CTRL),
+                }),
             }],
             alphabet: Default::default(),
         }