Merge pull request #229 from khawkins/unstable20

Merging unstable into unstable20
Updating submodules
What's new updates to README.md
Merge pull request #230 from khawkins/unstable_master_merge

Mobile SDK 1.5 release (unstable -> master)
Adding upgrade notes from 1.4 to 1.5
Merge pull request #232 from khawkins/upgrade_notes

Adding upgrade notes from 1.4 to 1.5
Updating versions, binaries
Merge pull request #233 from khawkins/unstable

Merging master into unstable
Merge remote-tracking branch 'upstream/unstable' into unstable20

Conflicts:
	dist/SalesforceSDK/SalesforceSDK-Debug.zip
	dist/SalesforceSDK/SalesforceSDK-Release.zip
	external/shared
	hybrid/SalesforceHybridSDK/SalesforceHybridSDK/Container/SFContainerAppDelegate.m
	native/SalesforceSDK/SalesforceSDK/Classes/SFRestAPI.m