use version from version.rb

exe/rat

···
 #!/usr/bin/env ruby
 
+$LOAD_PATH.unshift File.expand_path('../lib', __dir__)
+
 require 'didkit'
 require 'json'
 require 'minisky'
···
 require 'time'
 require 'uri'
 
-VERSION = '0.0.1'
+require 'ratproto/version'
 
 DID_REGEXP = /\Adid:[a-z]+:[a-zA-Z0-9.\-_]+\z/
 NSID_REGEXP = /\A[a-z0-9]+(\.[a-z0-9]+)+\z/
 
 def print_help
   puts <<~HELP
-    rat #{VERSION} 🦡
+    rat #{RatProto::VERSION} 🦡
 
     Usage:
       rat fetch at://uri
···
 when 'help', '--help', '-h'
   print_help
 when 'version', '--version'
-  puts "RatProto #{VERSION} 🐀"
+  puts "RatProto #{RatProto::VERSION} 🐀"
 when 'fetch'
   run_fetch(ARGV)
 when 'resolve'