Expanded Readme with section for Custom Data
Removed the assert from adding custom data; now logging an error and skipping the disallowed data.
Fixes IOS-304 Add custom data section to readme (person, device, message)
Merge branch 'master' into Next

Conflicts:
	README.md
Added methods to determine if the rating flow was shown.
`showRatingFlowFromViewControllerIfConditionsAreMet:` now returns a BOOL indicating if the rating flow was shown.
`ATAppRatingDidNotPromptForEnjoymentNotification` now sent when rating flow is not shown.
No Apptentive metrics are currently added for the event
Fixes IOS-340
Changed the default API Key string in FeedbackDemo
A string without spaces or braces can be entirely selected with a double-click.
Merge branch 'Next' into iOS7UIRefresh
Merge branch 'iOS7UIRefresh' of github.com:apptentive/apptentive-ios into iOS7UIRefresh