customized colors for names and hashtags (fixes #51)

[no6v]

I feel the following problems are there in this patch:

• keys must be a Symbol and case-sensitive
• cannot use combined color (ex. [36, 4] like :url)

[jugyo]

I'd be happy if it was a plugin. （標準機能として入れるべきか悩ましいですねぇ）

[no6v]

I see. I'll try.

[no6v]

Making it as a plugin, and closing this pull request at this time. https://gist.github.com/1652872 Enjoy!

[jugyo]

cool!