Removed growl & libnotify dependencies from gemspec

guard.gemspec

@@ -15,15 +15,11 @@ Gem::Specification.new do |s|
   s.required_rubygems_version = '>= 1.3.6'
   s.rubyforge_project = 'guard'
   
-  s.add_development_dependency  'rspec',       '~> 2.0.0'
+  s.add_development_dependency  'rspec',       '~> 2.0.1'
   s.add_development_dependency  'guard-rspec', '~> 0.1.3'
   
   s.add_dependency 'bundler',    '~> 1.0.2'
   s.add_dependency 'thor',       '~> 0.14.3'
-  # Mac OS X
-  s.add_dependency 'growl',      '~> 1.0.3'
-  # Linux
-  s.add_dependency 'libnotify',  '~> 0.1.3'
   
   s.files        = Dir.glob('{bin,images,lib}/**/*') + %w[LICENSE README.rdoc]
   s.executable   = 'guard'

lib/guard/notifier.rb

@@ -1,13 +1,6 @@
 require 'rbconfig'
 require 'pathname'
 
-case Config::CONFIG['target_os']
-when /darwin/i
-  require 'growl'
-when /linux/i
-  require 'libnotify'
-end
-
 module Guard
   module Notifier
     
@@ -17,9 +10,13 @@ module Guard
         title = options[:title] || "Guard"
         case Config::CONFIG['target_os']
         when /darwin/i
-          Growl.notify message, :title => title, :icon => image_path(image), :name => "Guard"
+          if growl_installed?
+            Growl.notify message, :title => title, :icon => image_path(image), :name => "Guard"
+          end
         when /linux/i
-          Libnotify.show :body => message, :summary => title, :icon_path => image_path(image)
+          if libnotify_installed?
+            Libnotify.show :body => message, :summary => title, :icon_path => image_path(image)
+          end
         end
       end
     end
@@ -41,5 +38,25 @@ module Guard
       end
     end
     
+    def self.growl_installed?
+      @installed ||= begin
+        require 'growl'
+        true
+      rescue LoadError
+        UI.info "Please install growl gem for Mac OS X notification support"
+        false
+      end
+    end
+    
+    def self.libnotify_installed?
+      @installed ||= begin
+        require 'libnotify'
+        true
+      rescue LoadError
+        UI.info "Please install libnotify gem for Linux notification support"
+        false
+      end
+    end
+    
   end
 end

spec/guard/notifier_spec.rb

@@ -7,6 +7,7 @@ describe Guard::Notifier do
     before(:each) { ENV["GUARD_ENV"] = 'special_test' }
     
     if mac?
+      require 'growl'
       it "should use Growl on Mac OS X" do
         Growl.should_receive(:notify).with("great",
           :title => "Guard",