Update podspec github URL.
IOS-519
Version tags are in the form of "v1.5.0". Added the "v".
IOS-519
Made "Powered By Apptentive" logo hidden and unclickable if `showTagLine == NO`.
Fixes IOS-522
Fixed iOS 6 tint color issue in Surveys. 96536294503f8b1f18e585ba5bc87ea977199d18
Oops, wrong selector. e81531816774beed26e7f705771799ff480f2457
Fixes IOS-523
The `locale_language_code` is now based on `[[NSLocale preferredLanguages] firstObject]` rather than the `NSLocaleLanguageCode` locale component.
Fixes IOS-525
Fix for CocoaPod inheriting the spec's prefix header contents when evaluating a subspec.
https://github.com/CocoaPods/CocoaPods/issues/2211
Updated API changes doc for v1.5.1.
Updated Changelog
Updated version to 1.5.1