Allow running specs even if Jeweler is not installed.

The check_dependencies task exists only when Jeweler is installed; if it is
not, don't add it as a dependency.

Rakefile

@@ -14,6 +14,8 @@ begin
     # gem is a Gem::Specification... see http://www.rubygems.org/read/chapter/20 for additional settings
   end
   Jeweler::GemcutterTasks.new
+
+  task :spec => :check_dependencies
 rescue LoadError
   puts "Jeweler (or a dependency) not available. Install it with: gem install jeweler"
 end
@@ -30,8 +32,6 @@ Spec::Rake::SpecTask.new(:rcov) do |spec|
   spec.rcov = true
 end
 
-task :spec => :check_dependencies
-
 task :default => :spec
 
 require 'rake/rdoctask'