Introduce a simple deprecatation mechanism in MSpec

* deprecate ruby_version_is A..B

Author: eregon

lib/mspec/guards/version.rb

@@ -1,3 +1,4 @@
+require 'mspec/utils/deprecate'
 require 'mspec/utils/version'
 require 'mspec/guards/guard'
 
@@ -9,6 +10,9 @@ def initialize(version)
     when Range
       a = SpecVersion.new version.begin
       b = SpecVersion.new version.end
+      unless version.exclude_end?
+        MSpec.deprecate "ruby_version_is with an inclusive range", 'an exclusive range ("2.1"..."2.3")'
+      end
       @version = version.exclude_end? ? a...b : a..b
     end
     self.parameters = [version]

lib/mspec/utils/deprecate.rb

@@ -0,0 +1,7 @@
+module MSpec
+  def self.deprecate(what, replacement)
+    $stderr.puts "\n#{what} is deprecated, use #{replacement} instead."
+    user_caller = caller.find { |line| !line.include?('lib/mspec') }
+    $stderr.puts "from #{user_caller}"
+  end
+end