Add Mutant::Version and --version flag for CLI

Closes #88

lib/mutant.rb

@@ -26,6 +26,7 @@ module Mutant
   EMPTY_STRING = ''.freeze
 end # Mutant
 
+require 'mutant/version'
 require 'mutant/cache'
 require 'mutant/node_helpers'
 require 'mutant/singleton_methods'

lib/mutant/cli.rb

@@ -265,7 +265,10 @@ module Mutant
       opts.separator ''
       opts.separator 'Options:'
 
-      opts.on('-r', '--require NAME', 'Require file with NAME') do |name|
+      opts.on('--version', 'Print mutants version') do |name|
+        puts "mutant-#{Mutant::VERSION}"
+        Kernel.exit(0)
+      end.on('-r', '--require NAME', 'Require file with NAME') do |name|
         require name
       end.on('--code FILTER', 'Adds a code filter') do |filter|
         add_filter Mutation::Filter::Code, filter

lib/mutant/version.rb

@@ -0,0 +1,5 @@
+module Mutant
+  # The current mutant version
+  VERSION = '0.3.0.beta22'.freeze
+end # Mutant
+

mutant.gemspec

@@ -1,8 +1,10 @@
 # encoding: utf-8
+#
+require File.expand_path('../lib/mutant/version', __FILE__)
 
 Gem::Specification.new do |gem|
   gem.name        = 'mutant'
-  gem.version     = '0.3.0.beta22'
+  gem.version     = Mutant::VERSION.dup
   gem.authors     = ['Markus Schirp']
   gem.email       = ['mbj@schirp-dso.com']
   gem.description = 'Mutation testing for ruby'