Clarify readme

[lf-]

I couldn't figure out from the readme how this is different from setting custom search keywords in Chrome: I've gone into the search engines list and set hoogle.haskell.org to !h so I can type !h query into my omnibox and search hoogle with it. This seems to implement the same or a similar thing? Or am I misunderstanding?

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[imskr]

@lf- This is much more than that. Right now we support only Twitter. With this you can go to any twitter account, search inside twitter etc. Soon I will be adding chrome extension and other commands such as github, mail etc.