Update README.md

Small changes to the English sentences, hopefully giving it a more natural feel.
Thank you very much for taking a look at the pull request.

You are correct regarding the usage of "discuss" . I have made a mistake.

Either way is fine, the options being:

Discuss how to install and use Hatohol

Discuss anything related to installing and using Hatohol.

Or

Discussion about how to install and use Hatohol

Discussion related to installing and using Hatohol.