Restructure contrib_bots bots to new layout.

In order to make the layout of all bots consistent, this commit
moves each bot into a folder with its name and modifies 'run.py'
so that only bots with such a structure can be executed. 'lib'
gets renamed to 'bots'.

contrib_bots/bots/tictactoe-bot/tictactoe/docs.md

@@ -0,0 +1,34 @@
+# About Tic-Tac-Toe Bot
+
+This bot allows you to play tic-tac-toe in a private message with the bot.
+Multiple games can simultaneously be played by different users, each playing
+against the computer.
+
+The bot only responds to messages starting with **@tictactoe** or **@ttt**.
+
+### Commands
+**@tictactoe new** (or **@ttt new**) will start a new game (but not if you are
+already playing a game.) You must type this first to start playing!
+
+**@tictactoe help** (or **@ttt help**) will return a help function with valid
+commands and coordinates.
+
+**@tictactoe quit** (or **@ttt quit**) will quit from the current game.
+
+**@tictactoe <coordinate>** (or **@ttt <coordinate>**) will make a move at the
+entered coordinate. For example, **@ttt 1,1** . After this, the bot will make
+its move, or declare the game over if the user or bot has won.
+
+Coordinates are entered in a (row, column) format. Numbering is from top to
+bottom and left to right.
+Here are the coordinates of each position. When entering coordinates, parentheses
+and spaces are optional.
+
+(1, 1)  | (1, 2) | (1, 3)
+
+(2, 1)  | (2, 2) | (2, 3)
+
+(3, 1)  | (3, 2) | (3, 3)
+
+Invalid commands will result in an "I don't understand" response from the bot,
+with a suggestion to type **@tictactoe help** (or **@ttt help**).