Major version bump to 2.0.0

While we are not testing RubyGems older then 2.0 for some while already
\[[1]\], this actually drops the compatibility layer and could in theory
break somebody.

[1]: 7b5fbc1

Author: voxik

lib/gem2rpm.rb

@@ -12,7 +12,7 @@
 require 'gem2rpm/test_suite'
 
 module Gem2Rpm
-  Gem2Rpm::VERSION = "1.0.2".freeze
+  Gem2Rpm::VERSION = "2.0.0".freeze
 
   class Exception < RuntimeError; end
   class DownloadUrlError < Exception; end