Fixed a lot of linter warnings

src/config.rb

@@ -1,18 +1,20 @@
+# frozen_string_literal: true
+
 require 'yaml'
 
+# Config - loads and manages the app's configuration
 class Config
 
   DEFAULT_CONFIG = 'config/defaults.yaml'
 
   def initialize(config_path)
-    @data = YAML::load_file(DEFAULT_CONFIG)
+    @data = YAML.load_file(DEFAULT_CONFIG)
 
-    if File.exists?(config_path)
-      @data.merge!(YAML::load_file(config_path))
-    end
+    # merge in user-defined configuration if it exists
+    @data.merge!(YAML.load_file(config_path)) if File.exist?(config_path)
   end
 
-  def get(key, depth = 0)
+  def get(key)
     bits = key.split('.')
     value = @data