Added clean task for removing build artifacts

rakefile.rb

@@ -34,6 +34,13 @@
   task :all => [:net45] do
   end
 
+  build :clean do |b|
+    b.prop 'configuration', $config
+    b.prop 'framework', 'NET45'
+    b.target = ['clean']
+    b.file = "source/#{PROJECT_NAME}.sln"
+  end
+
   build :net45 => ["nuget:restore", "version"] do |b|
     b.prop 'configuration', $config
     b.prop 'framework', 'NET45'
@@ -56,6 +63,11 @@
   tests.add_parameter "/xml=#{File.join(ARTIFACTS_PATH, "nunit-test-results.xml")}"
 end
 
+desc 'Cleans build artifacts'
+task :clean => 'build:clean' do
+  rm_rf ARTIFACTS_PATH
+end
+
 desc 'Builds release package'
 task :package => 'build:all' do
   include FileUtils