Add README note on recursive submodules

As libextobjc also contains submodules, git submodule add ... may not
pick them up automatically
Merge pull request #322 from js/patch-1

Add README note on recursive submodules
++expecta with changes from petejkim/master
dispose when the signal completes or errors
re-align the #if defs
test that it doesn't assert
better phrasing
Merge pull request #323 from ReactiveCocoa/dispose-when-completed

-toProperty:onObject: should dispose when the signal completes or errors
added -not
Merge pull request #327 from ReactiveCocoa/added-not

Added -not
Replace RACAsyncCommand example with an up-to-date one
Merge pull request #329 from ReactiveCocoa/readme-commands

Replace RACAsyncCommand example with an up-to-date one
Add a section about indentation style
Merge pull request #330 from ReactiveCocoa/signal-chain-style

Add a section about indentation style
Add a simple table of contents
Move Getting Started after the interesting stuff
Move RACExtensions mention to the Framework Overview
Title the ToC
Remove Foundation Support link
Move "When to use RAC" into the README