Release 0.3.0

• Rewrite lib/hello.rb.
• Add rake/*_task.rb files.
• Define new help task which is a default task.
• Define new task:all task which runs tests on multiple Ruby versions.
• Define new clean task instead of using rake/clean.
• Define new release:wizard task.
• Rename howto task to release:howto.
• Rename package task to gem:build.
• Rename release task to gem:publish.
• Include user account name into gemspec file.