Patch release for 3.7.0 with tvOS support

Updates

• bumped libwep version to 0.4.4

Features:

• added tvOS support #1327 and #1358 - fix #1368 and #1302

Fixes:

• #1217 contains several of the above fixes
• fix #391 -> option to cache only on Disk. will replace #1130
• fix #343 -> iCloud backup Option
• fix #371 -> CGBitmapContextCreate: unsupported parameter combination + #1268 #1412 #1340
• fix #576 -> scale set to screen scale
• fix #1035 -> progress queue with dispatch_async
• new feature -> activity indicator using auto layout. The activity indicator feature will replace #131
• #1218 progress callbacks now report on main thread - fixes #1035
• #1321 Added a new constructor to SDWebImagePrefetcher - replaces #956
• #976 append the original path extension to the hash filename - fixes #967
• replaced #999 with #1221
• added cache tests #1125
• #1236 fixes #1203
• bf899e2 fixes #1261 #1263 compilation issue CocoaPods vs non-CocoaPods
• #1367 fixes a bug where image scale & orientation are ignored when decoding / decompressing an image
• cac21e1 fixes #1366, addresses #1350 and reverts a part of #1221 - from commit 6406d8e, the wrong usage of dispatch_apply
• #1363 fixes #1361 sd_cancelBackgroundImageLoadForState
• #1348 Create a strong ref of weakOperation in the entry of The image download subOperation, use the strong ref instead weakOperation. At the same time, repair some logic of the 'If cancelled'
• dcb7985 replaces #1345 - Load local credential file
• #1323 don't to perform download if url is "" but not nil
• #1310 Added support for SDWebImageAvoidAutoSetImage option to UIButton and highlighted UIImageView categories
• #1308 Added Swift installation tips
• 32923fa Xcode 7.1 updates
• #1297 cleaner implementation of failedUrl error handling - fixes #1275
• #1280 Fix sd_animatedImageByScalingAndCroppingToSize
• Remove logging from the image prefetcher - #1276
• Fix typos #1256 #1257 #1258 #1331 #1290