Improve README structure, wordings and typo

Just a small contrib from me.

I have corrected most of the wordings and typos. I think it sounds and look much better now.

We should consider what information should be added in the README.

In overly general terms, there should be enough information to tell me whether the project is useful to me if all I know about it is the name. Don't assume anything about how the reader found it.

I suggest you add a section for "Versions". Just list down the high level but for the most part leave out the history of changes. It would be nice if you can list out a TODO or simple plan.

You should put the licence and terms as well.