Bumping REST API version up to v31.
Merge pull request #711 from khawkins/api_version_bump

Bumping REST API version up to v31.
Updating submodules, SDK version (to production)
Merge pull request #712 from khawkins/master

iOS: 2.3 Release
Merging master back to unstable
Merge pull request #713 from khawkins/unstable

iOS: Merging master back to unstable
What's new for 2.3
Hybrid upgrade steps
Post-create steps should probably be numbered
Some upgrade note revisions, based on feedback
Fixing wording
Fixing wording
Adding old upgrade notes back, as we'll save the previous version
Adding native upgrade steps, adding note about prior version upgrades
Merge pull request #716 from khawkins/readme

What's new for 2.3
Merge remote-tracking branch 'upstream/master' into unstable
Merge pull request #718 from khawkins/unstable

Mobile SDK: Merging master to unstable