Grammar fixes and improved README
I think this reads nicer and more accurately describes the HTTP reverse proxying.
## What is frp?
-frp is a fast reverse proxy to help you expose a local server behind a NAT or firewall to the internet. Now, it supports tcp, udp, http and https protocol when requests can be forwarded by domains to backward web services.
+frp is a fast reverse proxy to help you expose a local server behind a NAT or firewall to the internet. As of now, it supports tcp & udp, as well as http and https protocols, where requests can be forwarded to internal services by domain name.
## Table of Contents
