Move config file in own directory

lib/cross-post/config.rb

@@ -2,8 +2,11 @@ require 'yaml'
 
 class CrossPost
 	class Config
+		DEFAULT_CONFIG = File.join Dir.home, '.config/cross-post/config.yml'
+
 		def initialize
-			@file = ENV.fetch 'CROSS_POST_CONFIG', File.join(Dir.home, '.cross-post.yml')
+			@file = ENV.fetch 'CROSS_POST_CONFIG', DEFAULT_CONFIG
+			raise 'Unable to find config file' unless File.readable? @file
 			File.open(@file) { |f| @config = YAML.safe_load f }
 		end