Reading Railroad rules updates

I updated the "official" rules doc. for Reading Railroad in anticipation of the next playtest - which will be who-knows-when. Here's the current value of the things in flux:

* Start with 3 tiles in hand
* Turn options are
- - Make a word, get paid 1/3/6/10/15/21/28 coins for 2/3/4/5/6/7/8 letters
- - Buy track (costs vary) OR a Factory (cost 4 <- who knows if that's good?)
- - Draw tiles (1 + 1/4 city tiles). Factories count as 4 City tiles.
* Investor (!!!) tiles only hurt the player drawing.
- - Pay 1 coin/letter, take 1 debt for each letter you can't pay for.
* Investor (!!!) tiles are replaced
- - Always draw the right number of letter tiles each turn.
* Game ends when someone collects their 16th City tile from the board.
- - Factories count as 4 City tile toward this.
* Maximum total City tiles you can use is based on your largest connected network.
* Endgame words are free form.
- - Points are based on number of letters in the word, squared.
- - I still plan on having some sort of targeted endgame words in the end.