Better default values for Survey min/max required answers.
IOS-570
Added new App Store URL for iOS 7.1+ devices.
New URL opens "Reviews" tab directly, rather than the main App Store page.
Fixes IOS-567
Merge pull request #110 from apptentive/ratingURL7.1

Added new App Store URL for iOS 7.1+ devices.
Merge pull request #108 from apptentive/surveyDefaults

Better default values for Survey min/max required answers.
Merge branch 'Next' into french_canadian
Added authors to podspec
Fixes issue where text selection loupe showed through Message Panel to the view beneath.
Fixes IOS-342 and #94
Removed blurred background from Message Center.
Tweaked Message Center cell backgrounds to look better on a white background.
IOS-566
Merge pull request #114 from apptentive/loupe

Fixes issue where text selection loupe showed through Message Panel
Added methods for engaging events with `customData` and `extendedData`.
Added methods for sending Metrics with with `customData` and `extendedData`.
Store `data`, `customData`, and `extendedData` in the Event dictionary that formerly held `data`.
Store each under the correct key for server when adding to the dictionary, rather than later in `apiJSON`.
Added convenience methods for creating the initial `extendedData` types.
Added demo event with `customData` and `extendedData` to FeedbackDemo.
Added logging of 422 errors when `customData` or `extendedData` is malformed.
IOS-585
Not including `extendedData` keys if value passed in is `nil`.
Merge commit '3dde5f7b70545bd51533199347fcc1d754f4dec5'
Merge branch 'extendedData'
Changed the date/time `extendedData` method to take any arbitrary `NSDate`.
Updated example to use `extendedDataDate`.