Edit README.md of server and client

I installed hatohol client and server.
When I was installing there, I thought that README are need to fix.
Because, there are difficult to understand.
So, I fix some point and sent to this pull request.
On my browser (Safari on MacOS), this line is shown with the big letters. Probably '#' works as a 1st level caption. 

https://github.com/project-hatohol/hatohol/blob/edit-README-2/server/README.md