README: Improve links and intro

A slight reword of the intro, and a navigation bar above the intro to
quickly jump to the client repo or PS main.
Make sure that alts leave when a user is banned from a room
If a user is renamed, check if they are banned from their current rooms
Merge pull request #1021 from Slayer95/roomban

Fixes for room bans
Froslass is now banned from RU
http://www.smogon.com/forums/threads/np-ru-stage-1-dog-days-are-over-hello-kitty.3508302/page-10#post-5532624
Fix 3 move Jolteon/Raikou in Randbats

Removed hidden power grass from Jolteon and Raikou's movesets
Merge pull request #1022 from cometstorm/patch-4

Fix 3 move Jolteon/Raikou in Randbats
Update shop and bot commands
Update shop items
Update with `main` repo