Add tests back to Rakefile

Rakefile

@@ -1,6 +1,7 @@
+require 'rspec/core/rake_task'
 require File.dirname(__FILE__) + '/lib/haste/version'
 
-task :build do
+task :build => :test do
   system "gem build haste.gemspec"
 end
 
@@ -11,3 +12,8 @@ task :release => :build do
   # push the gem
   system "gem push haste-#{Haste::VERSION}.gem"
 end
+
+RSpec::Core::RakeTask.new(:test) do |t|
+  t.pattern = 'spec/**/*_spec.rb'
+  fail_on_error = true # be explicit
+end