Fix submodule clone command

Remove extra 'add'
Consistent folder name capitalization

vendor -> Vendor
Update submodules after adding them

Otherwise you have two empty folders in Vendor/
Merge pull request #137 from joemasilotti/submodules

Update submodules section of README
Merge pull request #136 from jbosse/master

Codesign for iOS
Add shorthand for pending.
Fix incorrect defines.
Fix errors in README.
Merge pull request #142 from paulyoung/pending-shorthand

Add shorthand for pending.